How many moles of ions are present

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In summary, the conversation discusses two different chemistry problems, one involving the calculation of moles of ions in a solution of sodium sulfate and the other involving the production of hydrogen gas through the decomposition of water using an electric current. The first problem was solved incorrectly because the number of ions produced by the dissociation of sodium sulfate was not taken into account. The second problem was solved correctly, but the number of electrons needed per molecule of hydrogen gas was not mentioned. The conversation ends with a reminder to read the forum rules before expecting quick responses.
  • #1
Asian Girl
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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
 
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  • #2
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).
 
  • #3
altegron said:
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
 
  • #4
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?
 
  • #5
How many electrons needed per each H2 molecule?

Borek
 
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  • #7


yea really I need answer for her question fast :S I have OLYMPIAD Tomorrow. Thanks :smile:
 
  • #8


Which question?
 
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  • #9


ElectroBoss said:
yea really I need answer for her question fast :S I have OLYMPIAD Tomorrow. Thanks :smile:
I'm sorry, but this forum does not work that way. Please read the forum rules first.
 

1. What is a mole of ions?

A mole is a unit of measurement used in chemistry to represent the amount of a substance. In the context of ions, a mole refers to the Avogadro's number (6.022 x 10^23) of ions.

2. How is the number of moles of ions calculated?

The number of moles of ions can be calculated by dividing the given amount of ions by the Avogadro's number. For example, if there are 1.2 x 10^24 ions present, the number of moles would be 1.2 x 10^24 / 6.022 x 10^23 = 1.99 moles.

3. What does the number of moles of ions tell us?

The number of moles of ions indicates the quantity of ions present in a substance or solution. It is used in chemical calculations and can help determine the amount of reactants and products in a chemical reaction.

4. Can the number of moles of ions change?

Yes, the number of moles of ions can change depending on the amount of substance present or the reaction taking place. It can also change with changes in temperature and pressure.

5. How does the number of ions in a substance affect its physical and chemical properties?

The number of ions in a substance can impact its physical and chemical properties. For example, a higher concentration of ions can affect the boiling and freezing points of a solution. The type and arrangement of ions can also determine the reactivity and behavior of a substance in chemical reactions.

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