CHEMICAL REACTIONS & EQUATIONS 10

  PRACTICE PAPER
CHEMISTRY  (2020) 

Class X                                 CHEMICAL REACTIONS & EQUATION

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I. Multiple Choice Questions 

1.  The reaction in which two or more reactants combine to form a single product is called

a. Displacement reaction

b. Combination reaction

c. Redox reaction

d. Oxidation reaction

2. Which of the following is not a physical change?

(a) Boiling of water to give water vapour

(b) Melting of ice to give water

(c) Dissolution of salt in water

(d) Combustion of Liquefied Petroleum Gas (LPG)

3.  Aqueous solution of two ionic compounds react by exchange of their ions is called

a.  Double displacement reaction.

b.  Displacement reaction.

c.   Combination reaction

d.  Nutralization reaction

 

4.  In which reactions, addition of oxygen or removal of hydrogen or loss of electron takes place.

a.  Redox reaction

b.  Reduction reaction

c.   Oxidation reaction

d.  None of the above

5. The following reaction is an example of a

4NH3(g) + 5O2 (g) → 4NO(g) + 6H2O(g)

(i) displacement reaction

(ii) combination reaction

(iii) redox reaction

(iv) neutralisation reaction

(a) (i) and (iv) (b) (ii) and (iii)

(c) (i) and (iii) (d) (iii) and (iv)

 

6.  If a substance gains hydrogen or loses oxygen during a reaction, it is said to be …

a.  Reducing agent or to be reduced

b.  Reducing agent or to be oxidised

c.   Reducing agent or oxidizing agent

d.  Oxidizing agent or to be reduced

 

7.  Process of slowly reacting up of metals due to attack of atmospheric gases is known as

a.  Rusting

b.  Corrosion

c.   Reduction

d.  Rancidity

8. Which of the following are exothermic processes?

(i) Reaction of water with quick lime

(ii) Dilution of an acid

(iii) Evaporation of water

(iv) Sublimation of camphor (crystals)

(a) (i) and (ii) (b) (ii) and (iii)

(c) (i) and (iv) (d) (iii) and (iv)

9.  When aluminium exposure to air, gets coated with a protective layer of

a.  Aluminium nitrate

b.  Aluminium oxide

c.   Aluminium sulphate

d.  Aluminium carbonate

   10. Which among the following is(are) double displacement reaction(s)?

        a. Pb + CuCl2 → PbCl 2 + Cu 

        b. Na2SO4 + BaCl2 → BaSO4 + 2NaCl

        c. C + O2 → CO2

        d. CH4 + 2O2 → CO2 + 2H2O

        (i) (a) and (d) 

        (ii) (b) only

        (iii) (a) and (b) 

        (iv) (c) and (d)

   11.  Which among the following statement(s) is(are) true? Exposure of silver    chloride to sunlight for a long duration turns grey due to

        a. the formation of silver by decomposition of silver chloride

        b. sublimation of silver chloride

        c. decomposition of chlorine gas from silver chloride

        d. oxidation of silver chloride

        (i) (a) only 

        (ii) (a) and (c)

        (iii) (b) and (c) 

        (iv) (d) only

   12. In the double displacement reaction between aqueous potassium

iodide and aqueous lead nitrate, a yellow precipitate of lead iodide

is formed. While performing the activity if lead nitrate is not

available, which of the following can be used in place of lead

nitrate?

    a. Lead sulphate (insoluble)

    b. Lead acetate

    c. Ammonium nitrate

    d. Potassium sulphate

   13. A chemical reaction can be observed with the help of any of the following    observations

 a. Evolution of a gas 

 b. Change in temperature and colour

 c. Formation of a precipitate

 d. Change in mass and property.

 (i). (a), (b) and (c)

 (ii). (a), (c), and (d)

 (iii).(a), (b), and  (d)

 (iv). (b), (c), and (d).

14. Which of the following statements about the given reaction are correct?3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g) 

  a. Iron metal is getting oxidised

  b. Water is getting reduced

  c. Water is acting as reducing agent

  d. Water is acting as oxidising agent

  (i) (a), (b) and (c) 

  (ii) (c) and (d)

  (iii) (a), (b) and (d) 

  (iv) (b) and (d)

15. Which of the following gases can be used for storage of fresh sample of an oil for a long time?

  a. Carbon dioxide or oxygen

  b. Nitrogen or oxygen

  c. Carbon dioxide or helium

  d.  Helium or nitrogen

16. Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form its solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed?

   a.  It is an endothermic reaction

   b.  It is an exothermic reaction

   c.  The pH of the resulting solution will be more than seven

   d.  The pH of the resulting solution will be less than seven

   (i).   (a) and (b) 

   (ii).  (b) and (c)

   (iii). (a) and (d) 

   (iv). (c) and (d)

17. A dilute ferrous sulphate solution was gradually added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears.Which of the following is the correct explanation for the observation?

    a. KMnO4 is an oxidising agent, it oxidises FeSO4

    b. FeSO4 acts as an oxidising agent and oxidises KMnO4

    c. The colour disappears due to dilution; no reaction is involved

    d. KMnO4 is an unstable compound and decomposes in presence

         of FeSO4 to a colourless compound.

18. Which of the following is(are) an endothermic process(es)?

   a.  Dilution of sulphuric acid

   b.  Sublimation of dry ice

   c.  Condensation of water vapours

   d.  Evaporation of water

  (i)   (a) and (c) 

  (ii)  (b) only

  (iii) (c) only 

  (iv) (b) and (c)

19. Which one of the following processes involve chemical reactions?

   a. Storing of oxygen gas under pressure in a gas cylinder

   b. Liquefaction of air

   c. Keeping petrol in a china dish in the open

   d. Heating copper wire in presence of air at high temperature.

20. In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?

   a.  2H2(l) + O2(l) → 2H2O(g)

   b.  2H2(g) + O2(l) → 2H2O(l)

   c.  2H2(g) + O2(g) → 2H2O(l)

   d.  2H2(g) + O2(g) → 2H2O(g)

21. Which of the following are combination reactions?

   a. 2KClO3 ⎯⎯⎯⎯→ Heat 2KCl + 3O2

   b. MgO + H2O ⎯→ Mg(OH)2

   c. 4Al + 3O2 ⎯→ 2Al2 O3

   d.  Zn + FeSO4 ⎯→ ZnSO4 + Fe

  (i) (a) and (c) 

  (ii) (c) and (d)

  (iii)(b) and (d) 

  (iv) (b) and (c)

22. Which of the following statement(s) is(are) correct about the

reaction?

   a.  It is a decomposition reaction and endothermic in nature

   b.  It is a combination reaction

   c.  It is a decomposition reaction and accompanied by release of heat

   d.  It is a photo chemical decomposition reaction and exothermic in nature

23. Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is

   a. 1:1

   b.  2:1

   c.  4:1

   d. 1:2

24. Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?

   a. Displacement reaction

   b. Precipitation reaction

   c. Combination reaction

   d. Double displacement reaction

   (i) (a) only 

   (ii) (b) only

   (iii) (d) only 

   (iv) (b) and (d)

   

II. Fill in the blanks 

    a.  If a change involves change in colour or state but no new substance is formed, then it is a …………..

b. In ………….. atoms in the reactants are rearranged to form one or more different substances.

c. ……………. lose their properties to form products of different properties.

d. During a chemical reaction, there is a breaking of bonds between atoms of the reacting molecules to give ……....

e. A ……….. reactive element displaces less reactive element from its aqueous salt solution.

f. In reductio reaction addition of ………. or removal of ………. or gain of electrons takes place.

g.  An acid and a base react together to form ……….and ………..

h. An oxidising agent gets ………. whereas a ……….. agent gets oxidised.

i. In terms of electronic concept, oxidation is defined as a …….. of electrons while reduction is defined as a ……. of electrons.

j. Corrosion in case of Iron is known as …..…..

k. When iron reacts with oxygen and moisture forms a red substance called ……....

l. Layer of ……………. protects the aluminium metal from further corrosion and damage.

m. .…… causes corrosion.

n. Rancidity can be prevented by adding …………..

III. True and False

a. The symbolic representation of a chemical reaction is called a chemical equation.

b. The arrow head points towards the reactants and indicates the direction of the reaction.

c. The reactants are written on the right hand side with a minus sign between them.

d. If heat is evolved during a reaction, then such a reaction is known as endothermic reaction.

e. Respiration is an endothermic reaction. 

f. A substance that loses oxygen or gains hydrogen is known as an reducing agent.

g. If a substance gains oxygen or loses hydrogen during a reaction, it is said to be oxidised.

h. Rust is a hydrated ferric oxide.

IV. Very short answer type questions: -

1. What is the skeletal equation?
2. What do you mean by rancidity?
3. Why it is necessary to balance a chemical equation?
4. Define oxidation and reduction.
5. What is S.I unit of electrical potential?
6. Name the gases evolved at anode and cathode on electrolysis of water. What is the ratio of gases?
7. Why do we store silver chloride in dark coloured bottles?
8. Why is hydrogen peroxide kept in colored bottles?
9. Why should the magnesium ribbon be cleaned before burning in air? 
10. What is meant by the endothermic reaction?
11. Differentiate between the reaction of magnesium and calcium with water  (giving an example).
12. Write the name of brown coloured gas that evolves when lead nitrate crystals are heated in a dry test tube. 
13. Which one is chemical change - rusting of iron or melting of iron?
14. Why do silver articles become black after sometimes when exposed to air?
15. Give reasons why chips manufacturers usually flush bags of chips with a gas such as nitrogen.
16. Write a balanced chemical equation for a chemical combination reaction.
17. What happened when ZnCO₃ is heated in the absence of air? Give the relevant equation.
18. Write the chemical equation for reactions that takes place when lead nitrate and potassium iodide solutions are mixed.
19. What happened when quicklime is added to water?
20. Name and state the law which is kept in mind while we balance chemical equations.
21. Give an example of a double displacement reaction.
22. Why decomposition reactions are called the opposite of combination reaction.
23. State one basic difference between a physical change and chemical change.
24. What is meant by a chemical reaction?
25. Is the burning of a candle wax a physical change or chemical change?
26. Why respiration considered an exothermic reaction?
27. Why photosynthesis is considered an endothermic reaction.
28. N₂ +H2 →2NH₃, name the type of reaction and write the balanced chemical equation.
29. Write the type of reaction in the a) rusting of iron and b) reaction between acid and base.
30. Name a reducing agent that may be used to obtain manganese from manganese dioxide.
31. Name the products formed on strongly heating ferrous sulfate crystal.

V. Short answer type questions: 

1. Define a chemical reaction. State two observation which helps us to determine that a chemical reaction has taken place. Write one example of each observation with a balanced chemical equation. 
2. What happens when dilute sulphuric acid is poured on Zinc granules?
3. Identify endothermic or exothermic reactions.
   (i) Decomposition of ferrous sulphate
   (ii) Dissolution of sodium hydroxide in water.
   (iii) Dissolution of ammonium chloride in water. 
4. Silver chloride turns grey when kept in sunlight. Give reason.
5. Grapes hanging on the plant do not ferment, but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change?
6. Why do fireflies glow at night?
7. What is corrosion? Name the compound formed when 
   (a) Silver corrodes (b) copper corrode.
8. When food containing fat or oil is not used and left for a long time they smell and taste changes. Name the process which is responsible for this change. List two methods to prevent or slow down the above change.
9. Write the balanced chemical equations and complete the following reaction and identify the type of reaction.
   (i) In thermite reaction, iron III oxide reacts with aluminum.
   (ii) Chlorine gas is passed in an aqueous potassium iodide solution.
10. Identify the type of chemical reaction and also write the chemical equation for the reaction that takes place when a solution of potassium chloride is mixed with silver nitrate solution. Write the chemical name of one of the products obtained.
    (i) In thermite reaction, iron III oxide reacts with aluminum.
    (ii) Chlorine gas is passed in an aqueous potassium iodide solution.
11. Write balanced chemical equations for the following reactions. 
    (a) Silver Bromide on exposure to sunlight decomposes into silver and bromine 
    (b) Sodium metal reacts with water to form sodium hydroxide and hydrogen gas.
12. Write balanced chemical equations for the following reactions.
    (i) Sodium bicarbonate on reaction with hydrochloric acids.
    (ii)Copper sulphate on treatment with potassium iodide.
13. On heating copper powder in the air, the surface of copper powder becomes coated with black CuO. How can this black coating be converted into brown copper? Write a chemical equation.
14. A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of reaction.
15. A solution of potassium iodide when mixed with lead nitrate solution, an insoluble substance is formed. 
    (a) Write the balanced chemical reaction involved and also mention the type of reaction.
    (b) What is the colour of the precipitate?
    (c) Name the compound precipitated.
16. State the reason, aluminum is more reactive than iron, yet its corrosion is less that of iron.
17. Write two observations that you will make when an iron nail is kept in an aqueous solution of copper sulphate. Write the chemical equation for this reaction.
18. Write the skeletal equation for the following reactions.
    (a) Hydrogen sulphide reacts with Sulpher dioxide to form Sulpher and water
    (b) Methane on burning combines with oxygen to produce carbon dioxide and water. What is the need of balance equations?
19. Identify the type of chemical reactions from the following equations: Displacement reaction, Combination,
    (a) CH₄ +2O₂ =CO₂ +2H₂O
    (b) CuSO₄ + Zn →ZnSO₄+ Cu   
    (c) CaO+H₂O→ Ca(OH)₂ 
    (d) Pb(NO₃)₂ +2KI= PbI₂ + 2KNO₃
20. When is a chemical reaction categorized precipitation reaction? Explain with two examples.
21. Write a balanced equation for the reaction between magnesium and hydrochloric acid. Name the product obtained, identify the type of reaction
22. Mention the colour of FeSO₄ .7H₂O crystals. How does this colour change upon heating? Give balanced chemical equations for the change.
23. What is a combination reaction.? state one example giving a balanced chemical equation for the reaction?
24. What is redox reaction? Identify the substance oxidized and the substance reduced in the reaction.
    (a) PbO+ C →2Pb+ CO.  
    (b) MnO₂ +4HCl→ MnCl₂ + 2H₂O + Cl_2.
25. Barium Chloride reacts with Aluminium Sulphate to give Aluminium Chloride and Barium sulphate.
    (a) State the two types in which the above reaction can be classified. 
    (b)Translate the above statement into a chemical equation.
26. A solution of substance X is used for whitewashing. 
    (a) Name the substance X and write its formula.
    (b) Express the reaction of X with water in the form of a balanced chemical equation.
27. (a) list any two changes which take place when oily food gets oxidized.  
    (b) Mention a measure which prevents or slows down its oxidation.
28. Translate the following statements into chemical equations and, then balance it:
    (a) Metal in the form of ribbon burns with a dazzling white flame and changes into a white powder.
    (b) In a test tube. Hydrochloric acid is poured over a few zinc granules. List two observations that suggest that a chemical reaction has occurred.  
29. Convert the following statements into balanced chemical equations: 
    (a) Zinc reacts with sulphuric acid to form zinc sulphate and hydrogen gas.
    (b) Magnesium burns in oxygen to form magnesium oxide.
30. (a) State the law which is followed in balancing a chemical equation.
    (b) Balance the following chemical equation. Fe + 2H₂O→ Fe₃O₄+ H₂
31. List 4 observations that help us to determine whether a chemical reaction has taken place: 
32. What is meant by a precipitation reaction? Explain by giving an example. Also, give a balanced chemical equation for the reaction stating the states of the reactions and the products formed. 
33. What happens when a piece of:
    (i) zinc metal is added to copper sulphate solution
    (ii) Silver metal is added to copper sulphate solution. Also write the balanced chemical equation, if a reaction occurs.

VI. Long answer type questions: 

1. A magnesium ribbon is burnt in oxygen to give a white compound X accompanied by the emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound Y.
   (i) Write the chemical formula of X and Y
   (ii) Write a balanced chemical equation when X is dissolved in water.
2. On heating blue coloured powder of copper II nitrate in a boiling tube, copper oxide(black), oxygen gas and brown gas X are formed.
   (i) Write a balanced chemical equation of the reaction.
   (ii) Identify the brown gas X evolved.
   (iii) Identify the type of reaction.
   (iv) What could be the pH range of aqueous solution of the gas X.
3. Write the balanced chemical equations for the following reaction and identify the type of reaction.
    (i) Sodium hydroxide solution is treated with acetic acid.
   (ii) Ethanol is warmed with ethanoic acid in the presence of sulphuric acid.
   (iii) Ethane is burnt in the presence of oxygen.
4. Identify endothermic or exothermic reactions.
   (i) CH₄ +2O₂ → CO₂ + H₂O
   (ii) CaO+ H₂O → Ca(OH)₂ .
   (iii) Dilution of an acid
   (iv) Evaporation of water
   (v) Sublimation of camphor.
5. Give the characteristics test for the following gases 
   (i) CO₂ (ii) SO₂ (iii)O₂ (iv) H₂.
6. What happens when zinc granules are treated with a dilute solution of H₂SO_4, HCL, HNO₃ NaCl and NaOH, also write the chemical equations, if a reaction occurs?
7. On adding a drop of Barium Chloride solution to an aqueous solution of sodium sulphate, a white precipitate is obtained.
   (i) Write a balanced chemical equation of the reaction involved
   (ii) What another name can be given to this precipitation reaction?
   (iii) On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?
8. Give reasons for the following:
   During the reaction of some metals with dilute hydrochloric acid, the following observations were made:
   (i) Silver metal does not show any change.
   (ii) The temperature of the reaction mixture rises when aluminium (Al) is added.
   (iii) The reaction of sodium metal is found to be highly explosive.
   (iv) Some bubbles of gas are seen, when lead (Pb) is reacted with the acid.
   (v) A gas is produced when sodium carbonate is added to the acid.
9. Write balanced chemical equations for the following reactions:
   (a) Dilute sulphuric acid reacts with Aluminium powder.
   (b) Dilute hydrochloric acid reacts with sodium carbonate.
   (c) Carbon dioxide is passed through lime water.
10. (a) Give an example for a combination reaction which is exothermic
    (b) Identity oxidizing agent in the following reaction. 
    H₂S+Cl₂ → 2HCl + S
    (c) Name the phenomenon due to which the taste and smell of oil change when kept for a long time in open. Suggest one method to prevent it.
11. I. What is rancidity? Mention any two ways by which rancidity can be prevented.
    II. Write balanced chemical equations for the reactions that take place during respiration. Identify the type of combination reaction that takes place during this process and justifies the name. Give one more example of this type of reaction.
12. In the electrolysis of water
    (a) Name the gas collected at the cathode and anode respectively.
    (b) Why is the volume of one gas collected at one electrode double that at the other? Name this gas.
    (c) How will you test the evolved gases?
13. Name the salts that are used in black and white photography. Give reactions when they are exposed to light. Define the type of chemical reactions taking place.
14. I. A small amount of calcium oxide is taken in a beaker and water is added slowly to it
    (a) Will there be any change in temperature of the contents? Explain.
    (b) Name and define what type of reaction taking place.
    (c) Write chemical equations for the above reaction.
     II. A substance X which is an oxide of a group 2 element, is used intensively in the cement industry. This element is present in bones also. On treatment with water, it forms a solution that turns red litmus blue. Identify X and also write the chemical reactions involved.
15. 2g of ferrous sulphate crystals are heated in a boiling tube.
    (a) State the colour of ferrous sulphate crystal both before heating and after heating.
    (b) Name the gases produced during heating
    (c) Write the chemical equation for the reaction.
16. Describe an activity to show a decomposition reaction in which light is used to decompose reactants. Write the chemical equation of the reaction and state its one use.
17. Give reasons for the following:
    (a) All decomposition reactions are endothermic reactions.
    (b) Color of copper sulphate solution change when an iron nail is dipped in it.
    (c) Respiration is an exothermic reaction.
18. A brown substance X on heating in the air forms a substance Y. When hydrogen gas is passed over heated Y it again changes back into X. (a) name the substances X and Y.
    (b) name the chemical process of occurring during both the changes.
    (c) Write the chemical equations involved in both the changes.
19. 2g of Lead Nitrate powder is taken in a boiling tube. The boiling tube is heated over the flame. Now answer the following:
    (a) State the colour of the fumes evolved and the residue left.
    (b) Name the type of chemical reaction that has taken place stating its balanced equation.
20. When a chemical reaction considered a double displacement reaction? Explain by giving an example. 
    State a difference between displacement and double displacement reaction.
21. (a) What is an oxidation and reduction reaction? Identify in the following reaction, the substance oxidised and the substance reduced.
    ZnO + C = Zn + CO.
    (b) State the meaning of oxidation in a chemical reaction. Consider the chemical reaction represent by the following equation and write the name of the substance oxidized or reduced, oxidizing agent and reducing agent in the reaction.  MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂
22. Differentiate between a combination reaction and a decomposition reaction. Write one chemical equation each for this reaction.
23. The student takes 2 gm of ferrous sulphate crystal in a dry test tube and heats the test tube. Answer the following questions on the basis of observations made by the student:
    (a) Write an observation about colour of residue or smell of gas evolved.
    (b) Name the type of chemical reaction                                               (c) Write a balanced chemical equation for the reaction involved.
24. Differentiate between an exothermic reaction and an endothermic reaction. Write one example for each one of these reactions in the form of a balanced chemical equation.
25. A combination reaction is the reverse of a decomposition reaction. Justify this statement with the help of appropriate chemical equations of each.
26. In the following. Chemical reaction zinc oxide reacts with carbon to produce Zinc metal and carbon monoxide. ZnO + C → Zn + CO
    (a) Identify the substance getting oxidized and getting reduced.
    (b) State the reason for choosing the substances in (a).
    (c) Name the type of reaction and give another example of a similar type of reaction.
27. A decomposition reaction required energy in the form of heat or electricity. Give one example of each.
28. A student takes Na₂CO₃ powder in a test tube and pours some drops of acetic acid in it. He observes: 
29. I. Aqueous solution of sodium sulphate and barium Chloride reacts as follows :ZnSO₄ +BaCl₂→ BaSO₄  + 2NaCl.
    (a) Identify the type of reaction
    (b) Define the type of reaction
    (c) Suggest another name for this reaction.
    II. (b) Giving one example of each, define the following terms:
    (a) Corrosion  (b)Rancidity.
30. (a) Most of the metals acquired a dull surface when exposed to air. Name the chemical phenomenon responsible for this process.
    (b) State the conditions under which the iron articles get rust. Design an activity to investigate the conditions necessary for rusting. Suggest any two methods to prevent rusting of iron.
31. I. Accounts for the following:
    (a) Paint is applied to the Iron article
    (b) Oil and fat containing food items are flushed with nitrogen.
    (c) When Iron nails kept in copper sulphate solution, the blue colour of the solution fades and Iron nails become brownish.
    II. Account for the following:
    (a) White silver chloride turns grey in sunlight. 
    (b) Brown colored copper powder on heating in the air turns into a black-colored substance.
32. What do you mean by?
    (a) Displacement reaction
    (b) Reduction reaction.
    (c) Oxidation reaction.
    (d) Decomposition reaction.
    (e) Combination reaction? 
    Explain with suitable example.
33. I. Solid calcium oxide was taken in a container and water was added slowly to it.
    (a) Write the observation,
    (b) Write the chemical formula of the product formed.
    II. What happens when carbon dioxide gas is bubbled through lime water?
    (a) In a small amount
    (b) In excess?
34.  I. (a) Why do you apply Paint on Iron articles?
    (b)What happens chemically when quicklime is added to water.
    (c) Balance the following chemical equation. MnO₂ +HCl→MnCl₂+Cl₂+H₂O.
    II. Give one example each of a chemical reaction described by:
    (a) evolution of gas
    (b) change in colour
    (c) formation of precipitate
    (d) change in temperature.
    (e) change in state.
35. Balance the following equations :
    (i) Hg(NO₃)₂ ⎯⎯⎯→Hg + NO₂ + O₂ heat.
    (ii) NaNO3 ⎯⎯⎯→NaNO2 + O₂ he
    (iii) Ca + H₂O ⎯⎯→ Ca(OH)₂ + Heat
    (iv) NaNO₃ + H₂SO₄→ Na₂SO₄+ HNO₃   
    (v) Na₂CO₃ + H₂O + CO₂ ⎯⎯→ NaHCO₃
    (vi) Mg + HCl ⎯⎯→ MgCl₂ + H₂
    (vii) Na +H₂O ⎯⎯→ NaOH + H₂
    (viii) C₄H₁₀ + O₂⎯⎯→ CO₂ + H₂O
    (ix) FeS + HCl ⎯⎯→ FeCl₂ + H₂S
    (x) MnO₂ + HCl ⎯⎯→MnCl₂+H₂O + Cl₂
    (xi) Mg₃N₂ + H₂O ⎯⎯→ Mg(OH)₂ + NH₃
    (xii) NH₃ + O₂ → N₂ + H₂O
    (xiii) MgCl₂ + Na₂CO₃ →NaCl+ MgCO₃
    (xiv) NaOH +  → NaCl + NaClO + H₂O
    (xv) FeCl3 + NaOH → NaCl + Fe(OH)₃
    (xvi) NaCl + MnO₂ +H₂SO4→NaHSO₄+ MnSO₄ + H₂O + Cl₂
    (xvii) KNO₃ + H₂SO₄→ K₂SO₄ + HNO₃
    (xviii) PbO + HNO₃ → Pb(NO₃)₂ +H₂O
    (xix) FeSO₄ + NaOH → Na₂SO4+ Fe(OH)₂
    (xx) Fe₂(CO₂)₃ + H₂SO₄ →Fe₂(SO₄)₃ +  CO₂ + H₂O
    (xxi) Ca(OH)₂ + HNO₃ ⎯→ Ca(NO₃)₂ + H₂O
    (xxii) BaCl₂ + H₂SO₄ → BaSO₄ + HCl
    (xxiii) H₂SO₄ + NaOH → Na₂SO4+ H₂O
    (xxiv) NaCl + AgNO₃ → AgCl + NaNO₃
    (xxv) Al + Fe₂O₃ → Al₂O₃ + Fe
    (xxvi) Cl₂ + P₄ → PCl₅
    (xxvii) CH₄ + O₂ → CO₂ + H₂O
    (xxviii) Pb(NO₃)₂ → PbO + NO₂ + O₂