Is Matter Around Us Pure — Science STD 9 — Question

Iron powder and sulphur powder were mixed together and divided into two parts A and B. When part A was heated strongly over a burner, then a substance C was formed. The part B was, however, not heated at all. When dilute hydrochloric acid was added to substance C, then gas D was evolved and when dilute hydrochloric acid was added to part B then gas E was evolved.

1. What type of substance is B?
2. What type of substance is C?
3. Name the gas (i) D, and (ii) E?
4. Write one characteristic property of gas D.

Which has more atoms, 50g of aluminium or 50g of iron? Illustrate your answer with the help of calculations.
(Atomic masses: Al = 27u; Fe = 56u)

Name the following compounds. Also write the symbols/ formulae of the ions present in them:

1. CuSO₄
2. (NH₄)₂SO₄
3. Na₂O
4. Na₂CO₃
5. CaCl₂

One of the forms of a naturally occurring solid compound P is usually used for making the floors of houses. On adding a few drops of dilute hydrochloric acid to P, brisk effervescence are produced. When 50g of reactant P was heated strongly, than 22g of a gas Q and 28g of a solid R were produced as products. Gas Q is the same which produced brisk effervescence on adding dilute HCl to P. Gas Q is said to cause global warming whereas solid R is used for white-washing.

1. What is (i) solid P (ii) gas Q, and (iii) solid R.
2. What is the total mass of Q and R obtained from 50g of P?
3. How does the total mass of Q and R formed compare with the mass of P taken?
4. What conclusion do you get from the comparison of masses of products and reactant?
5. Which law of chemical combination is illustrated by the example given in this problem?

When extremely small particles X derived from the another of a flower were suspended in a liquid Y and observed through a microscope, it was found that the particles X were moving throughout the liquid Y in a very zig zag way. It was also observed that warmer the liquid Y, faster the particles X moved in its surface.

1. What could particles X be?
2. What do you think liquid Y is?
3. What is the zig-zag movement of particles X?
4. What is causing the zig-zag movement of particles X?
5. Name the scientist who discovered this phenomenon.
6. What does this experiment tell us about the nature of liquid Y?

How would you prepare a saturated solution of sodium chloride in water at 25°C? What will happen if this solution is cooled to 10°C?

In an experiment, 4.90g of copper oxide was obtained form 3.92g of copper. In another experiment, 4.55g of copper oxide gave, on reduction, 3.64g of copper. Show with the help of calculations that these figures verify the law of constant proportions.

List five characteristics by which compounds can be distinguished from mixtures.

Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).

Substance Dissolved	Temperature in K
	283	293	313	333	353
	Solubility
Potassium nitrate	21	32	62	106	167
Sodium chloride	36	36	36	37	37
Potassium chloride	35	35	40	46	54
Ammonium chloride	24	37	41	55	66

1. What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313K?
2. Pragya makes a saturated solution of potassium chloride in water at 353K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.
3. Find the solubility of each salt at 293K. Which salt has the highest solubility at this temperature?
4. What is the effect of change of temperature on the solubility of a salt?