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How do you calculate the moles of ELECTRONS !!

1.

What is the number of moles of electrons in 0.357 g of gold?

2.

Mg(s) + Ni2+(aq) --> Mg2+(aq) + Ni (s) What is the total number of moles of electrons needed to completely reduce 6.0 moles of Ni2+(aq) ions?

(edited 7 years ago)
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Original post by Adorable98

1.

What is the number of moles of electrons in 0.357 g of gold?

2.

Mg(s) + Ni2+(aq) --> Mg2+(aq) + Ni (s) What is the total number of moles of electrons needed to completely reduce 6.0 moles of Ni2+(aq) ions?



The stoichiometric equation gives you the ratio of moles. If two electrons are lost by one species with a coefficient of 1 then the number of moles of electrons is 2 x 1.

Example:

Zn --> Zn2+ + 2e

If you have 0.1 moles of zinc then 0.1 x 2 moles of electrons are lost.
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Avatar for Adorable98
Adorable98
OP
15
Original post by charco
The stoichiometric equation gives you the ratio of moles. If two electrons are lost by one species with a coefficient of 1 then the number of moles of electrons is 2 x 1.

Example:

Zn --> Zn2+ + 2e

If you have 0.1 moles of zinc then 0.1 x 2 moles of electrons are lost.


I see, so for b(ii) OH- has one electron so how does it end up having 10 moles of electrons :s-smilie:??

And for Q1, how do I workout the moles of electrons in 0.357g of gold,
I worked out the moles : 0.357/197 = 1.81x10-3 mol then do I multiply it by the number of electrons Au has,
so 1.81x10-3 x 79?

And for Q2, I have no idea what to do?:redface:
Original post by Adorable98
I see, so for b(ii) OH- has one electron so how does it end up having 10 moles of electrons :s-smilie:??

Hydroxide has the formula OH-
draw out the Lewis structure and oxygen has four pairs of electrons in the valence shell plus 2 electrons in the inner shell.
(4 x 2) + 2 = ?

Original post by Adorable98

And for Q1, how do I workout the moles of electrons in 0.357g of gold,
I worked out the moles : 0.357/197 = 1.81x10-3 mol then do I multiply it by the number of electrons Au has,
so 1.81x10-3 x 79?

:smile:
Original post by Adorable98

And for Q2, I have no idea what to do?:redface:

:frown:

1 nickel ion requires 2 electrons for reduction ...
(edited 7 years ago)
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Avatar for Adorable98
Adorable98
OP
15
Original post by charco
Hydroxide has the formula OH-
draw out the Lewis structure and oxygen has four pairs of electrons in the valence shell plus 2 electrons in the inner shell.
(4 x 2) + 2 = ?


:smile:

:frown:

1 nickel ion requires 2 electrons for reduction ...

Oh okay so 2x6 = 12 moles of electrons.

Now I get it! Thank you so much!!
(edited 7 years ago)
For the first one work out how many moles of gold you have. Then multiply it by the number of electrons in gold to work out the total number of moles of electrons in the gold.
For the second one oxygen has 8 electrons hydrogen has 1 and it's a negative ion so that's 1 more so 10 electrons per ion of OH- therefore 1 mole of OH- will have 10 moles of electrons.

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