GUESS QUESTIONS CLASS 10TH CHAPTER 1

GUESS QUESTIONS

EXPECTED MARKS: 2-3

BALANCING OF CHEMICAL RAECTIONS

1.    Why should a magnesium ribbon be cleaned before burning in air?

2.    State any 2 observations in an activity which may suggest you that a chemical reaction has taken place. Give examples to support your answer.

3.    What is a balanced chemical equation? Why should chemical equations be balanced? on what basis is the chemical reaction balanced?

4.    Write a balanced chemical equation with state symbols for the following reactions.Also identify the type of reaction in following examples:

a)    Hydrogen + Chlorine → Hydrogen chloride

b)    Barium chloride + Aluminium sulphate → Barium sulphate +Aluminium chloride

c)     Sodium + Water → Sodium hydroxide + Hydrogen

d)    Iron+ water-> iron oxide+ hydrogen.

e)     Ferrous sulphate decomposes to give ferric oxide , sulphur dioxide and sulphur trioxide.

f)     Lead nitrate decomposes to give lead oxide + nitrogen di-oxide and oxygen.

g)    Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.

h)    Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.

i)     Magnese dioxide and hydrochloric acid reacts to give magnese chloride , chlorine and water.

j)     Hydrogen gas combines with nitrogen to form ammonia.

k)    Hydrogen gas combines with oxygen to form water.

l)     Hydrogen sulphide gas burns in air to give water and sulpur dioxide.

m)   Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

n)    Potassium metal reacts with water to give potassium hydroxide and hydrogen gas

o)    Iron + copper sulhpateà iron sulphate + copper.

p)    Nitric acid +slaked lime ->calcium nitrate and water

q)    Aluminium and copper chloride gives aluminium and copper.

r)     HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O

s)     NaOH + H2SO4 → Na2SO4 + H2O

t)     NaCl + AgNO3 → AgCl + NaNO3

u)    BaCl2 + H2SO4 → BaSO4 + HCl

v)    Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water

w)    Zinc + Silver nitrate → Zinc nitrate + Silver.

x)    Barium chloride solution is mixed with copper sulpate solution and a white precipitate is observed.

y)    On heating copper powder in iar in a china dish, the surface of copper powder turns balck.

z)    On heating green coloured ferrous sulphate crystals, reddish brown solid is left and smell of gas having odour of burning sulphur is experienced.

aa) Iron nails when left dipped in blue copper sulphate solution becomes brownish in colour and the blue colour of copper sulphate fades away.

bb) Quick lime reacts vigorously with water releasing a large amount of heat.

COMBINATION REACTIONS

5.    A solution of a substance ‘X’ is used for white washing.(i) Name the substance ‘X’ and write its formula.                       ii) Write the reaction of the substance ‘X’ named in (i) above with water.

OR

Solid calcium oxide was taken in a container and water was added to it.

(i)           State 2 observations made in the experiment.

(ii)          Write the name and chemical formula of the product formed. What happens when CO2 is passed through this product.

OR

What happens chemically when quick lime is added to water.

OR

A housewife wanted her house to be whitewashed. She bought 10 KG of quick lime from the market and dissolved it in 30 litres of water. On adding lime to water, she noticed that the water started boiling even when it was not being heated. Give reason for her observation. Write the corresponding chemical equation and name the product formed.

6.    A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.

DECOMPOSTION REACTION

7.    What do you mean by decomposition reaction? Describe an activity to illustrate such a reaction by heating.

8.    Write 2 equations each for decomposition reactions where energy is supplied in the form of heat, light or electricity.

9.    What happens when ferrous sulphate crystals, limestone and lead nitrate is heated. is any similarity in these reactions.

10. What change in colour is observed when silver chloride is left exposed to sunlight ? what type of chemical reaction is this.

11. Why is the amount of gas collected in one of the test tubes in electrolysis of water is double of the amount collected in the other? Name this gas.

DISPLACEMENT REACTION

12. What happens when dilute hydrochloric acid is added to iron fillings.

13. Which gas is liberated and how will you test for that gas which is liberated when hydrochloric acid reacts with active metals.

14. Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

15. What do you mean by thermite reaction? Which category of reaction is this?

16. In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.

DOUBLE DISPLACEMENT REACTION

17. Explain double displacement reaction along with 5 important examples.

18. What is the difference between displacement and double displacement reactions? Write equations for these reactions.

19. What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube ? what type of reaction is this.

PRECIPITATION REACTION.

20. What do you mean by a precipitation reaction? Explain by giving examples.

OXIDATION AND REDUCTION

21. Identify the substances that are oxidised and the substances that are reduced in the following reactions.

(i)           4Na(s) + O2(g) → 2Na2O(s)

(ii)          CuO(s) + H2(g) → Cu(s) + H2O(l)

(iii)        2PbO(s) + C(s) → 2Pb(s) + CO2(g)

(iv)         Zn+C à Zn+CO

(v)          MnCl2+4HCl-_MnCl2+Cl2+H2O

22.  Why the shining surface of some metals becomes dull when exposed to air for a long time.

23. Name a reducing agent that may be used to obtain manganese from manganese dioxide.

24. Explain the following in terms of gain or loss of oxygen with two examples each.

(i)           Oxidation

(ii)          Reduction.

RANCIDITY

25. Explain rancidity and the methods to prevent rancidity.

26. Oil and fat containing food items are flushed with nitrogen. Why.

OR

Potato chips manufacturers fill the packet of chips with nitrogen gas. ?

CORROSION

27. Explain corrosion and the methods to prevent it.

28. Why do we apply paint on iron articles?

EXOTHERMIC AND ENDOTHERMIC REACTION

29. Distinguish between exothermic and endothermic reactions by giving examples. Amongst the following reactions, identify the exothermic reaction and endothermic reaction.

(i)            Heating coal in air to form carbon dioxide.

(ii)          Heating limestone in a lime kiln to form quick lime.

(iii)        Decomposition of vegetable matter into compost.

30. Why is respiration considered an exothermic reaction.

31.  Is oxidation an exothermic or endothermic reaction?