Question

what is the mass in grams of 17.56 mL of acetone, which has the density of 0.7857 g/cm^3

Answer 1

1 mL = 1 cm^3, so 17.56 mL = 17.56 cm^3
Multiply the volume by the density to get the mass.

Answer 2

so would i divide 0.7857 by 17.56 to get 0.04474? it has to be expressed in four significant figures

Answer 3

How did "Multiply the volume by the density to get the mass." become a division problem?

Answer 4

ok, i wasnt sure if that was your final answer, it didnt seem right.

Answer 5

so expressed in four sf it would be 13.80?

Answer 6

nevermind thank you, forgot that cm^3 and g/mL are same diff.. lol, was making it more complicated than it actually was, thanks for your help!!

Answer 7

13.80 is correct bec of the 4 sf as you stated.

Answer 8

thanks for your help, lol, dont know what i was thinking..

Answer 9

When you do calculations with numbers that have units attached to them, keep the units with the numbers, and carry out the calculations with the units.

Let's say you can't tell whether you need to multiply the two given numbers or divide the two given numbers. By keeping the untits, it'll help you figure it out.

When you multiply these two amounts together, cm^3 cancels out, and you get an answer in g (grams), which makes sense because you're looking for a mass.

If you divide the numbers the way you did, the units turn out to be g/cm^4 which is meaningless.