# How many moles of ions are present

• Chemistry
Asian Girl
I thought this is a pretty easy problem and I can't believe I did it wrong. What did I do wrong?

How many moles of ions are present in 250mL of 4.4 M solution of sodium sulfate?

Here what I did:
250 mL = .25 L
mol Na2(SO)4 = MV = 4.4 * .25 = 1.1 mol

but the answer was 3.3 mol

altegron
Because the question asks how many ions are present, you need to multiply the moles of sodium sulfate by the number of ions it breaks down into in water.

In this case, I believe the Na2(SO)4 will dissociate to make two Na+ ions and one (SO)4 ion (total of 3 ions).

Asian Girl
Because the question asks how many ions are present, you need to multiply the moles of sodium sulfate by the number of ions it breaks down into in water.

In this case, I believe the Na2(SO)4 will dissociate to make two Na+ ions and one (SO)4 ion (total of 3 ions).

Thanks

Asian Girl
Another one:
Water can be decomposed by the passage of an electric current according to the equation 2H2O (l) ---> 2H2 (g) + O2 (g)
How many moles of H2 (g) can be produced from the passage of 4.8*10^21 electrons?

I solved:
4.8*10^21 / 6.022*10^23 * 2 = 1.6*10^-2 mol

What did I do wrong?

Mentor
How many electrons needed per each H2 molecule?

Borek

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ElectroBoss

yea really I need answer for her question fast :S I have OLYMPIAD Tomorrow. Thanks

Mentor

Which question?

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Staff Emeritus