Paper : ICSE Class X Important Questions : Chemistry (2003)

General Instructions

1. Section I is compulsory. Attempt any four questions from Section II.
2. The intended marks for questions or parts of questions are given in brackets [ ].

SECTION I (40 Marks)
Attempt all questions from this Section

Question 1

(a) (i)What volume of oxygen is required to burn completely a mixture of 22.4 dm³ of methane and 11.2 dm³ of hydrogen into carbon dioxide and steam? Equations of the reactions are given below (Assume that all volumes are measured at S.T.P )

CH₄ + 2O₂ → CO₂ + 2H₂O

2H₂ + O₂ → 2H₂O

(ii) The gases hydrogen‚ oxygen, carbon dioxide, sulphur dioxide and chlorine are arranged in order of their increasing relative molecular mass. Given 8g of each gas at STP, which gas will contain the least number of molecules and which gas the most? [5]

(b) Match the description in column X with the appropriate substance in column Y. Write down the number of the description with the letter of the substance. The first one has been done for you.

The first answer is 1-G. [10]

(c) (i) How would you distinguish between Zn²⁺ and Pb²⁺ using ammonium hydroxide solution?

(ii) Copy and complete the following table which refers to the action of heat on some carbonates [5]

(d) Copy and complete the following table which refers to two practical applications of electrolysis- [5]

(e) Choosing the correct words given in brackets, complete the sentences given below: [5]

1. An acid is a compound which, when dissolved in water, gives............ (hydronium/hydroxide) ions as the only .............(positive/negative) ions.
2. Electrolysis is the passage of .................(electricity/electrons) through a liquid or a solution accompanied by a............ (physical/chemical) change.
3. Allotropy is the property of a (n) ...................(compound/element) which can exist in two more than two forms in the same ................ (chemical/ physical) state.
4. A (n) .............. (acid/basic) salt is one in which the hydrogen of an acid has been partially replaced by .............. (metal/non-metal).
5. The number of atoms present in one .................. (mole/molecule) of an element is called its .................. (acidity/atomicity)

(f) Write the observations and balance the equations for the following reactions: [10]

1. Sodium hydroxide is added drop-wise till in excess to a solution of zinc sulphate.
2. Ammonium hydroxide is added first in a small quantity and then in excess to a solution of copper sulphate.
3. Excess of ammonium hydroxide is added to a substance obtained by adding hydrochloric acid in silver nitrate solution.
4. Moist starch iodide paper is put on the mouth of a test-tube containing chlorine gas.
5. A paper dipped in potassium permanganate solution is put on the mouth of a test-tube containing sulphur dioxide gas.

SECTION II (40 marks)
Answer any four questions from this section

Question 2

(a) 10g of a mixture of sodium chloride and anhydrous sodium sulphate is dissolved in water. An excess of barium chloride solution is added and 6·99g of barium sulphate is precipitated according to the equation given below-

Na₂SO₄+ BaCl₂→ BaSO₄₊ 2NaCl
(O = 16; Na = 23; S = 32; Ba = 137)
Calculate the percentage of sodium sulphate in the original mixture. [4]

(b) (i) Which compound should be heated with soda lime to obtain ethane gas in the laboratory?

(ii) Write the equation for the reaction in 2(b) (i) above.

(iii) Write a balanced equation for the complete combustion of ethane.

(iv) Name a solid which can be used instead of concentrated sulphuric acid to prepare ethylene by the dehydration of ethanol.

(v) Name a reagent which can be used to distinguish between ethane and ethene.

(vi) Ethylene forms an addition product with chlorine. Name this addition product and write its structural formula. [6]

Question 3
The following table represents the first three periods of the modern periodic table. Study the table and answer the questions that follow:[10]

(a) Write the formula of the sulphate of the element with number 13.

(b) What type of bonding will be present in the oxide of the element with atomic number 13.

(c) Which feature of the atomic structure accounts for the similarities in the chemical properties of the elements in group 7A of the periodic table ?

(d) Name the element which has the highest ionization potential.

(e) How many electrons are present in the valency shell of the element with the atomic number 18?

(f) What is the name given to the energy released when an atom in its isolated gaseous state accepts an electron to form an anion?

(g) What is the electronic configuration of the element in the third period which gains one electron to change into an anion?

(h) Fill in the blanks:
The atomic size ............ as we move from left to right across the period, because the ............... increases but the ........... remains the same.

Question 4

(a) (i) Write the equation for the formation of ammonia by the action of water on magnesium nitride.

(ii) How is ammonia collected?

(iii) Why is ammonia not collected over water?

(iv) Which compound is normally used as a drying agent for ammonia? [4]

(b) (i) When nitric acid is prepared by the action of concentrated sulphuric acid on potassium nitrate, what is the special feature of the apparatus used?

(ii) Write the equation for the laboratory preparation of nitric acid from potassium nitrate and concentrated sulphuric acid.

(iii) Potassium nitrate is prepared from potassium hydroxide and nitric acid. Name the type of this reaction.

(iv) Which gas is produced when potassium nitrate is heated? Write the equation for the reaction. [6]

Question 5

(a) Complete the sentences (i) and (ii) and answer the questions (iii) and (iv).

1. Chlorine is prepared in the laboratory by the .............. (state the type of reaction) of ............... hydrochloric acid.
2. Chlorine is a ............... (state the colour) gas which is .............. than air.
3. Bleaching powder (CaOCl₂) smells like chlorine due to the action of carbon dioxide on it. Write the equation for the reaction.
4. Write the balanced equation for the action of chlorine with excess of ammonia. [5]

(b) (i) Iron has valencies 2 and 3. When iron reacts directly with chlorine what is the valency of iron in the resulting compound? Write the equation for the same.

(ii) Name a non-metallic element which reacts with chlorine to give two compounds. Under normal conditions one of these compounds is a liquid the other is a solid. Name the two compounds. [5]

Question 6

(i) Write equations for sulphur combining directly with:

1. A metal
2. A non-metal.

(ii) Which concentrated acid will oxidize sulphur directly to sulphuric acid? Write the equation for the same.

(iii) What is the name of the process by which sulphuric acid is manufactured? Name the catalyst used in the process.

(iv) Complete the following sentence choosing the correct word from the brackets.
"Concentrated sulphuric acid is used in the laboratory preparation of nitric acid and hydrochloric acid because it is ............(less volatile/stronger) in comparison to these two acids." [6]

(b) Write the equations for the laboratory preparation of the following salts using sulphuric acid:

1. Iron (II) sulphate from iron.
2. Copper sulphate from copper.
3. Lead sulphate from lead nitrate.
4. Sodium sulphate from sodium carbonate [4]

Question 7

(a) With respect to the reduction of iron-ore in the blast furnace, answer the following questions:

1. Name the raw material placed in the blast furnace.
2. Which is the actual reducing agent? Write the equation for the reduction of iron-ore.
3. What is the significance of double cup and cone arrangement?
4. What is the composition of the exiting furnace gases? [6]

(b) Compare the properties of a typical metal and a non-metal on the basis of the following:

1. Electronic configuration.
2. Nature of the oxides.
3. Oxidising or reducing action.
4. Conductivity of heat and electricity. [4]