Important questions for Class 10 Chemistry6:54 pm
Chemistry has always been a major part of science for the class 10 students. Its not very difficult to score good marks in chemistry if you learn the basic theory and have practice of the chemical formulas. Based on the studies made on the previous years questions we have picked some very important questions for class 10 Chemistry. These questions have been frequently asked in the board exams of past years.
Q1. From the following list of substances, choose the substances which meet the description given in parts (i) to (v) below :
Ammonium chloride, ammonium nitrate, chlorine, dilute hydrochloric acid, iron, lead nitrate, manganese (IV) oxide, silver nitrate, sodium nitrate, sodium nitrite, sulphur
i. Two compounds heated together in solution to produce nitrogen.
ii. An element which exists in two crystalline forms.
iii. A compound which on heating gives oxygen as the only gaseous product.
iv. A substance containing both molecules and ions.
v. Two compounds whose aqueous solution give white precipitates with dilute Hydrochloric acid.
Q2. What do you see when:
i. Sodium hydroxide solution is added to zinc sulphate solution till it is in excess.
ii. Chlorine water is exposed to sunlight.
iii. Ammonia gas is bubbled through red litmus solution.
iv. Barium chloride solution is added to dilute sulphuric acid.
Q3. Explain why the following statements are not correct:
i. The element nitrogen can be obtained in the pure state by removing carbon dioxide and oxygen from air.
ii. Ammonium salts will, on heating, decompose to give ammonia.
iii. Lead chloride can be prepared by adding dilute hydrochloric acid to lead
iv. 1 gram of any gas occupies 22.4 liters at S.T.P.
Q4. i. A solution has a pH of 7. Explain how you would:
1. Increase its pH;
2. Decrease its pH.
ii. If a solution changes the color of litmus from red to blue, what can you say?
About its pH
iii. What can you say about the pH of a solution that liberates carbon dioxide from
Q5. i. Under the same conditions of temperature and pressure you collect 2 litres of
carbon dioxide, 3 litres of chlorine, 5 litres of hydrogen, 4 litres of nitrogen and
1 litre of sulphur dioxide. In which gas sample will there be:
1. The greatest number of molecules;
2. The least number of molecules? Justify your answer.
ii. The pressure on one mole of gas at S.T.P. is doubled and the temperature is
raised to 546 K. What is the final volume of the gas?
iii. Find the total percentage of oxygen in magnesium nitrate crystals:
(H = 1 , N = 14 , O = 16 , Mg = 24)
Q6. You are given the three white powders calcium carbonate, lead carbonate and
zinc carbonate. Describe the tests you would carry out in solution to identify the
metal in each of the above compounds. Indicate clearly how you would prepare the
solutions for the tests.
Q7. Write the equation for each of the following reactions:
i. Action of heat on potassium nitrate.
ii. Chlorine is passed over heated iron.
iii. Chlorine is passed into pure water.
iv. Solutions of ammonium chloride and sodium hydroxide are mixed and heated.
v. Copper sulphate solution is added to sodium hydroxide solution.
Q8. What is the purpose of the Haber Process?
ii. Name the gaseous inputs of the Haber Process and state the ratio by volume
in which the gases are mixed.
iii. What is done to increase the rate of the reaction in the Haber process?
iv. Give two different ways by which the product can be separated from the
Q9. A compound contains 87.5% by mass of nitrogen and 12.5% by mass of
Hydrogen. Determine the empirical formula of this compound.
(a) Choose the letters A, B, C or D to match the descriptions from (i) to (vi) given below:
A. Ammonia B. Hydrogen Chloride
C. Hydrogen sulphide D. Sulphur dioxide.
i. This gas can be oxidized to sulphur.
ii. This gas decolourises potassium permanganate solution.
iii. When this gas is bubbled through copper sulphate solution, a deep blue coloured solution is formed.
iv. This gas gives a white precipitate when reacted with silver nitrate solution
acidified with dilute nitric acid.
v. This gas burns in oxygen with a green flame.
vi. This gas can be obtained by the reaction between copper and concentrated
Q10. When heated, potassium permanganate decomposes according to the following equation:
2KMnO4+K2MnO4+ MnO2 + O2
(i) Some potassium permanganate was heated in a test tube. After collecting one litre of oxygen at room temperature it was found that the test-tube had undergone a
loss in mass of 1.32 g. If one litre of hydrogen under the same conditions of temperature and pressure has a mass of 0.0825 g, calculate the relative molecular mass of oxygen.
(ii) Given that the molecular mass of potassium permanganate is 158, what volume of oxygen (measured at room temperature) would be obtained by the complete decomposition of 15.8 g of potassium permanganate? (Molar volume at room temperature is 24 litres .
Q11. Periodic Table are as follows with the elements arranged in alphabetical order:
Al Cl Mg Na P S Si
1.5 3.0 1.2 0.9 2.1 2.5 1.8
(i) Arrange the elements in the order in which they occur in the Periodic Table from left to right. (The group 1 element first, followed by the group 2 element and so on, upto group 7.)
(iii) Choose the word or phrase from the brackets which correctly completes each of the following statements.
i. The element below sodium in the same group would be expected to have a…………. (lower/higher) electronegativity than sodium and the Y element above chlorine would be expected to have a …………… (lower/higher) ionization potential than chlorine.
ii. On moving from left to right in a given period, the number of shells………… (remains the same/increases/decreases).
iii. On moving down a group, the number of valence electrons…………. (remains the same/increases/decreases).
Q12. Name from the list of substances given below, the substances which you would use to prepare each of the following salts, named in parts from (i) to (iv):
The substances are:
(Copper, Lead, Sodium, Zinc, Copper oxide, Lead carbonate, Sodium carbonate solution, Dilute hydrochloric acid, Dilute nitric acid and Dilute sulphuric acid):
i. Zinc sulphate;
ii. Copper sulphate;
iii. Sodium sulphate;
iv. Lead sulphate.
Q13. Sulphur dioxide and chlorine are both used as bleaching agents:
i. What is similar in the use of chlorine and sulphur dioxide as bleaching agents?
ii. How does the bleaching action of these two gases differ?
iii. What type of fibre should not be bleached using chlorine? Why should the use of chlorine be avoided for this fibre?
Q14. Write balanced equations for the following reactions:
i. Chlorine is passed into an aqueous solution of sulphur dioxide.
ii. Aluminium powder is warmed with hot and concentrated caustic soda solution.
iii. Concentrated nitric acid is added to copper turnings kept in a beaker.
iv. Red lead (trilead tetroxide) is warmed with concentrated hydrochloric acid.
v. Chlorine gas is passed through an aqueous solution of iron (II) sulphate
acidified with dilute sulphuric acid.
Q15. Which of the following methods A, B, C, D or E is generally used for preparing the chlorides listed below from (i) to (v). Answer by writing down the chloride and the letter pertaining to the corresponding method. Each letter is to be used only once.
A. Action of an acid on a metal
B. Action of an acid on an oxide or carbonate
C. Direct combination
D. Neutralization of an alkali by an acid
E. Precipitation (double decomposition)
(i) Copper (II) chloride (ii) Iron (II) chloride
(iii) Iron (III) chloride (iv) Lead (II) chloride
Q16. (i) Name the ore of zinc containing its sulphide.
(ii) In the process of extracting zinc, the above named ore is roasted. Write the equation for the reaction which takes place when the sulphide ore is roasted.
(iii) Name the substance used to reduce the roasted ore. Write the equation for the reaction.
i. The moles of sulphur dioxide present in the flask.
ii. The number of molecules of sulphur dioxide present in the flask.
iii. The volume occupied by 3.2g of sulphur dioxide at S.T.P.(S = 32, 0 = 16)
Q17. Aluminium is extracted from its chief ore, Bauxite. The ore is first purified and the metal is extracted from it by electrolytic reduction.
i. Write three balanced equations for the purification of bauxite by Hall’s process.
ii. Name a chemical used for dissolving aluminium oxide. In which state of subdivision is the chemical used?
iii. Write an equation for the reaction which takes place at the anode during the extraction of aluminium by the electrolytic process.
iv. Mention one reason for the use of aluminium in thermite welding.
Q18. (i) Write the equation for the reaction in the Haber process that forms ammonia.
(ii) State the purpose of liquefying the ammonia produced in the process.
(iii) Predict the group of an element X if its atomic number is 16.
(iv) State one reason why tap water is not used to prepare a solution of silver nitrate
Q19. (i) Write the equation for the preparation of ethylene from ethyl alcohol.
(ii) Write the general formula for a saturated hydrocarbon and give one example of a saturated hydrocarbon with its structural formula.
(iii) Name a compound which will give acetylene gas when treated with water.
Q20. Which particular property of cast iron makes it unsuitable for the construction of bridges?
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