[lokobreed]

A solution that is 11% iron chloride by mass has a density of 1.149g/mL. What mass of iron chloride, in grams, is present in 2.50 L of this solution.

I thought I knew how to do this problem, but I am confused.

D=M/V so 1.149g/ml = 11 g/V - Volume would then equal 9.573, so 1.149g/ml=11g/9.573ml

If I set that up correctly, how do I figure out how man grams is present in 2.50 L of this solution?

D=M/V - Volume would be 2500 ML right?

[rabolisk]

D=M/V so 1.149g/ml = 11 g/V - Volume would then equal 9.573, so 1.149g/ml=11g/9.573ml

That is unnecessary. But you are right about the volume of the solution being 2500 mL. Do you know what they mean by 11% by mass?

[lokobreed]

11% mass means out of 100 parts means that 11 of them are iron chloride... correct? like 11g out of 100g?

[rabolisk]

Yes. So you have volume of solution, density of solution, and the mass percentage of iron chloride. You are asked to find the mass of iron chloride. The logical steps would be volume(soln)  mass(solution) mass (iron chloride)

[lokobreed]

ok thanks

so the density then would remain the same
so... 1.149g/ml=287.25g/2500ml correct?

Then how would i convert that into mass of chloride only? would i multiply 287.25 x .11 = 31.5975 g then w/ Signficant Figures be 31.597

[rabolisk]

Don't you mean 2872.5 grams? Also, your final sig figs should be 3 because you started out with 3.

[lokobreed]

yes i meant that. so  the answer would be  315.975 and if 3 SIG Figures would be 315.9 ?

where did you get three from?

in the book they have the answer as 3.2 x 10^2??? any idea as to why?

[rabolisk]

I missed the 11% part. That's where the 2 sig figs come from, and why the answer is 3.2 x 10^2 g, as opposed to 3.16 x 10^2 g (316 g).

[lokobreed]

ok but if i took 2872.5 x .11 = 315.975 wouldnt that convert it to the grams of chloride in the solution?

so why am i moving the decimal point to 3.2

[rabolisk]

3.2 * 10^2 grams = 320 grams. I suggest you brush up on your scientific notation.

[lokobreed]

wow - i think i was just overly confused lol


Thanks again