(a)(i) Draw and label a diagram for the laboratory preparation of a dry sample of sulphur(IV)oxide.
(ii) Write a balanced chemical equation for the reaction in (a)(i).
(iii) State the precaution that must be taken in the preparation of the gas stated in (a)(i).
(iv) Give a reason why the precaution stated in (a)(ii) must be taken.
(b)(i) State Dalton's law of partial pressures.
(ii) The volume of a sample of methane collected over-water at a temperature of 12°C and a pressure of 700 mmHg was 30cm\(^3\). Calculate the volume of the dry gas at s.t.p. [Saturated vapour pressure of water at 12°C is 10 mmHg] •
(c)(i) Write an equation for the reaction between chlorine and water.
(ii) Why does litmus paper turn red when put in the resulting solution in (c)(i)?
(d)(i) State the trend in the boiling points of chlorine, bromine and iodine.
(ii) Explain briefly why water has a higher boiling point than ammonia.
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Discussions (7)
@Mosunmolaishola, from the question, we were told the gas (methane) was collected over water, which means the gas would still contain some water vapour . However, we were asked to calculate the volume of the dry gas(no water vapour should be present), the reason we must subtract the standard vapour pressure of water which was given as 10mmHg @ the same temperature the gas was collected, i.e 12°C.
The pressure with which the gas was collected was 700mmHg but we need the pressure of the dry gas, so subtract the vapour pressure of water from the total pressure so you can get the actual pressure used in collecting the dry methane gas. Hence, P1 = 700 - 10 = 690mmHg
I hope you now understand.
