Answer :
The total vapour pressure of a solution is 110mmHg which is calculated using Raoult's law. The mole fraction of substance A is given as 0.35, and the vapour pressures of pure A and B are given as 87 mmHg and 122 mmHg.
According to Raoult's law, the partial pressure of a component in a solution is proportional to its mole fraction. The mole fraction of substance A is 0.35, which means that it constitutes 35% of the solution. Therefore, the contribution of substance A to the total vapour pressure is 0.35 times its vapour pressure, which is 0.35 * 87 mmHg = 30.45 mmHg.
Similarly, the contribution of substance B can be calculated as 0.65 times its vapour pressure, which is 0.65 * 122 mmHg = 79.3 mmHg.
To find the total vapour pressure, we add the partial pressures of A and B: 30.45 mmHg + 79.3 mmHg = 109.75 mmHg.
Rounding this value to the nearest whole number, we get 110 mmHg. Therefore, the correct answer is option a) 110 mmHg.
Learn more about Raoult's law here:
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