Rohini tested the solubility of five substances at different temperatures. She noted the amount of each substance dissolved in 100g of water to form a saturated solution at a particular temperature and reported the following data:
Substance
A
B
С
D
E
Temperature
35°C
21.4
25.0
7.9
40.6
62.0
20°C
18,6
20.0
8.2
36.2
32.0
50°C
23.8
35.0
7.6
45.4
106.0
(a) Which substance is least soluble in water at 35°C?
(b) Which substance is most soluble in water at 20°C?
(c) What mass of B would be needed to make a saturated solution in
(d)
(e)
200g of water at 20°C? What amount of E would separate out when 106.0g of its solution at 50°C is cooled to 20°C?
Do all solutions show the same effect of temperature on the solubility of the salt?
Answers
Explanation:
ANSWER
(a) At 313 K 62 g of potassium nitrate dissolved in 100 g of water. So to produce a saturated solution of potassium nitrate in 50 g of water we need
100
62
×50=31 g of potassium nitrate.
(b)Some soluble potassium chloride will separate out in the form of crystal at room temperature because the solubility of potassium chloride will decrease.
(c)
(i) Solubility of Potassium nitrate at 293 K is 32 g.
(ii) Solubility of sodium chloride at 293 K is 36 g.
(iii) Solubility of Potassium chloride at 293 K is 35 g.
(iv) Solubility of Ammonium chloride at 293 K is 37 g.
The solubility of Ammonium chloride is highest at this temperature.
(d)The solubility of salt increases with the increase in temperature.