Question

Which has a greater volume: 1000g of water or 1000g of ethanol? i found it and put in in sig figs (because we're always supposed to) and the volumes are both 1000mL. should i say they're equal, or base it off the actual values w/o considering sig figs?

Answer 1

`rho` `(H_2O) = 1.00` `g` `cm^-3`;

`rho` `(H_3C-CH_2OH) = 0.79` `g` `cm^-3`. Are you sure your conclusions are correct?

Explanation:

As a physical scientist, you should always consult the literature to find the correct physical properties. You have equal masses of water, and ethanol. As you know, you do not have an equal number of moles. The densities of the pure solvents are markedly different.

As a follow up, what would happen if you drank both quantities? In one case you would be dead!

Answer 2

You need more significant figures in your mass measurement.

Explanation:

The density of water is `1.0000 "g/cm"^3"`, and the density of ethanol is `0.789 "g/cm"^3"`. It is impossible for `1000 "g"` of each to have the same volume.

The problem is that your mass measurement `1000 "g"` has only one significant figure. You need more significant figures. Because you have to round your volume to 1 sig fig, it appears as if 1000 g of water and 1000 g of ethanol have the same volume, which is false.

Redo your mass measurement. Whenever you make a measurement, record what you observe plus one more estimated digit. This will make the measurement more accurate and give you more sig figs.

If the masses you gave initially were exactly `1000 "g"`, then you should have recorded the masses as `1000.0 "g"`, giving you 5 sig figs. This would have given you a volume of `1.0000 "L"` of water and `1270 "L"` of ethanol.