Question

Hello, everyone! I need really appreciate some help with a chemistry assignment. The homework question is below; no rush!

Calculate the mass of ammonium sulfide (NH4)2S in 3.00 L of a 0.020 M solution.

Answer 1

Find the moles then the mass

\(\sf Molarity=\dfrac{moles}{L}\)

then

\(\sf moles=\dfrac{mass}{Molar~mass}\)

Answer 2

Thanks, Aaron!

I had a bunch of equation written down, but they were confusing me. I'll try that! (:

Thanks again!

Answer 3

no problem!

Answer 4

This is what I did so far:

\[M = 0.020\div3 = .0066\]

Then:

\[moles = .0066\div68.154 = 9.7\]

Is my answer correct, along with my significant figures @aaronq?

Thanks (:

Answer 5

the first step is wrong, you solved for molarity instead of moles.

Answer 6

rearranged, the formula is \(\sf moles=Molarity*L\)

Answer 7

Oh, okay.

What should the first equation be with numbers plugged in?

I don't even have the moles yet, do I?

I think I mistook the M (molarity) for moles.

In order to find the moles, do I use this equation, @aaronq ?

\[grams = mol/gram\]

So, converting liters to grams then finding molar mass?

\[3000 g = 1 mol/ 68.1 g (NH4)2S\]

Answer 8

nope. you use the equation i posted originally.

You were given molarity and volume (in L

\(\sf Molarity =\dfrac{moles}{L}\rightarrow moles=Molarity*L=0.020 ~M* 3 L=0.060 ~moles\)

then \(\sf moles=\dfrac{mass}{Molar~mass}\rightarrow mass=Molar~Mass*moles=0.060 ~moles*68.1 ~g/mol\)

Answer 9

btw, "grams=mol/gram" is not correct.

how can that be equal?

Answer 10

Thank you!

I got 4.08, but unfortunately forgot to round it up to 4.09.

Thank you so much, @aaronq!

I'm really sorry for all of my questions.

Answer 11

No worries, that's why were here.

I'm glad you got it figured out though!