The vapour pressure of pure benzene at a certain temperature is 0.850 bar. A non volatile, non electrolyte solid weighing 0.5 g is added to 39.0g of benzene. The vapour pressure of the solution then is 0.845 bar. What is the molecular mass of the solid substance

The molar mass is 169g / mol.

Explanation:

To achieve this result you must consider the formula:

[(pº-p) / pº] = [na / (na + nb)]

This formula should be replaced by the values shown in the question as follows:

pº = 0.850 bar

p = 0.845 bar

To find the values of "na" and "nb", we will consider that the letter "m" represents the molecular mass of benzene that is equal to 78, so we have:

na = 0.5 / m; nb = 39/78 = 0.5

Now we can replace all values in the formula:

0.850-0.845 / 0.850 = (0.5 / m) / (0.5 / m) +0.5 =

0.5 / (0.5 = 0.5m) =

1/1 + m =

m = 0.850 / 0.005 - 1 = 169g / mol

in this passage from chapter 6 of "animal farm", by george orwell, what the author is ridiculing in this passage is the frivolity of some rules.

clover, the mare, believes she remembers that the fourth commandment forbade sleeping in beds because it was something that humans did. snowball, napoleon, and the pigs are brain-workers who look after the welfare of the farm. they are the obvious leaders because they are smart, and so they are entitled to eat the best food and sleep in beds. it is squealer, who says these lines making the difference between sleeping with sheets, what humans do, and sleeping in beds, what pigs do. the unwillingness to question authority makes the oppressed to obey without thinking.