Question

I have to solve this problem for chemistry:

An empty vial weights 55.32g. If the vial weighs 185.56g when filled with liquid mercury, what is its volume. (Assuming the density of liquid mercury is 13.5)

My teacher told me the answer is 9.6747g, however, he didn't round the answer based on the number of sig digs the least precise measurement has. 13.5 is the least precise measurement with only 3 sig digs, however, my teacher didn't change his answer to reflect that. He said the final answer can just have the same number of sig digs as the original measurement (in this case 185.56g). Is that the standard for the amount of sig digs you use when calculating density? Or is it just a preference thing?

Answer 1

9.65 ml of mercury or 9.6474 ml

Step-by-step explanation:

Assuming the units of density are g/ml for mercury,

density = mass/volume

• rearrange equation in terms of volume

volume = mass/density

• subtract mass of empty vial from mass of vial + mercury

volume = (185.56g-55.32g)/13.5g/ml

volume = 9.6474 ml

9.65 ml with correct sig figs.

• Note: I calculated a slightly different answer from your teacher.

The unit for this answer would be in ml or L.

Technically, the answer for this problem would be in 3 sig figs because you are limited by 13.5, however your teacher probably wants the focus of this problem to be on calculating density instead of sig figs. This is common with some teachers but is not the standard for calculating density.