Question

How many initial moles are there of ethyl acetate according to this information? How do you calculate it?
Volume = $ {{5}}{{.00}} $ mL
Density = $ {{0}}{{.893}} $ g/mL
Molar mass (M) = $ {{88}}{{.11}} $ g/mol

Answer 1

Hint: In the above question, we are asked to find out the number of moles of ethyl acetate is present when volume, density and molar mass is given. Here, we don’t have to use any specific formula. Here just simple conversion is required. We find the mass of ethyl acetate and use it to find the number of moles.

Formula Used: $ {{moles}} = \dfrac{{{\text{mass}}}}{{{\text{molar mass}}}} $

Complete step by step solution
In the above question, volume, density and molar mass is given. The density is given as $ {{0}}{{.893}} $ g/mL, volume is given as $ {{5}}{{.00}} $ mL and molar mass is given as $ {{88}}{{.11}} $ g/mol.
From density, we can infer that:
When volume is 1 mL, the weight of ethyl acetate present = $ {{0}}{{.893}} $ g
Since, the volume given is 5mL, so,
When volume is 5 mL, the weight of ethyl acetate present = $ {{0}}{{.893 \times 5 = 4}}{{.465}} $ g
From molar mass, we can infer that:
In $ {{88}}{{.11}} $ g, ethyl acetate constitutes 1 mole.
In $ {{4}}{{.465}} $ g, ethyl acetate constitute $ \dfrac{{{1}}}{{{{88}}{{.11}}}}{{ \times 4}}{{.465 = 0}}{{.05}} $ .
The initial moles present in ethyl acetate is $ {{0}}{{.05}} $ moles of ethyl acetate according to the given information.

Note
In the above question, we may have discussed how to proceed through the ideal gas equation. But the pressure is not given, hence, we cannot proceed in that way. In these types of questions where you don’t have any clue as to how to proceed, then, look at the units of each of the quantities given and then you can by simple manipulation can get the desired result.