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2001 - Multiple Choice - Q14 - HSN forum

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2001 - Multiple Choice - Q14


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#1 tupacshakur

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Posted 27 May 2005 - 11:27 AM

wondering if you can help me on this question.

Higher chem 2001 Multi choice question 14

The Avogardo Constant is the same as the number of:

a) molecules in 16g of oxygen

b) electrons in 1g of hydrogen

c) atoms in 24g of carbon

d) ions in 1 litre of sodium chloride solution concentration 1 mol

i got A as the answer but its wrong. The right answer is B but i dont know why that is the answer.

p,ease help
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#2 dfx

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Posted 27 May 2005 - 11:36 AM

Well, you're looking for L particles of a substance, or ONE MOLE of particles.

in 16g of Oxygen, there's half a molecule (1 molecule of Oxygen is 32 grams - O2)... so its L/2 particles.

in 24g of Carbon, there's 2L atoms cause 1L atoms of Carbon is 12g. So this isnt it either.

I don't know about (d), but as for the right answer (b) L particles for Hydrogen atoms/electrons is 1g because its atomic mass is 1g...

I know I'm not making too much sense... lol.. but this topic was always damn confusing if thats any consolation biggrin.gif

#3 YIC

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Posted 27 May 2005 - 11:46 AM

but I thought 1g hydrogen would be 0.5 moles (since it is H2 so gfm=2).
So wouldn't there be L/2 electons?

#4 bred

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Posted 27 May 2005 - 11:54 AM

Hydrogen is diatomic so in 2g it has 2 moles of atoms, and thus 2x as many electrons. The gfm of hydrogen is 1 but as it is diatomic it's mass is 2g per mole of molecules.
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#5 tupacshakur

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Posted 27 May 2005 - 12:02 PM

is the correct calculation not, (for [b] electrons in 1g of hydrogen)

1g/2gfm = 0.5mol

0.5mol x 6.02 times 10^23

= 3.01 times 10^23

3.01 times 10^ 23 x 1 electron

= 3.01 times 10^23 electrons?
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#6 bred

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Posted 27 May 2005 - 12:19 PM

But I thought the answer was B?
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#7 YIC

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Posted 27 May 2005 - 12:19 PM

I understand now!!!

1 mole of hydrogen would be 6.02 x 10^23 MOLECULES but 1.024 x 10^23 ATOMS. This means that 0.5 mol (i.e 1 g) would have 6.02 x 10^23 atoms and therefore 6.02 x 10^23 electrons!

#8 tupacshakur

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Posted 27 May 2005 - 12:22 PM

s the correct calculation not, (for [b] electrons in 1g of hydrogen)

1g/2gfm = 0.5mol

0.5mol x 6.02 times 10^23

= 3.01 times 10^23

3.01 times 10^ 23 x 1 electron

= 3.01 times 10^23 electrons?

how is that wrong???
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#9 bred

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Posted 27 May 2005 - 12:22 PM

YIC - Don't you mean 1.204x10^24 atoms?

Tupac - It's 0.5 moles of molecules but 1 mole of atoms and therefore 1 mole of electrons, right?
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#10 tupacshakur

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Posted 27 May 2005 - 12:25 PM

QUOTE(bred @ May 27 2005, 12:22 PM)
YIC - Don't you mean 1.204x10^24 atoms?

Tupac - It's 0.5 moles of molecules but 1 mole of atoms and therefore 1 mole of electrons, right?

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yeah but we are talking about electrons not atoms or molecules.
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#11 dfx

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Posted 27 May 2005 - 12:26 PM

The way I see it. Since 2g = 1 MOLECULE = L MOLECULES, therefore 1g = 1 ATOM = 1 mole of electrons = L.

#12 tupacshakur

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Posted 27 May 2005 - 12:28 PM

can someone write out the equation or calculation they would use to get B as the answer?
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#13 bred

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Posted 27 May 2005 - 12:31 PM

2g hydrogen = 2 moles atoms = 2 moles electrons = 2 avogadros
thus, 1g hydrogen = 1 mole electrons = 1 avogadros
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#14 dfx

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Posted 27 May 2005 - 12:38 PM

Fully fledged genius indeed. Well put! lol. biggrin.gif

#15 YIC

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Posted 27 May 2005 - 02:28 PM

QUOTE(bred @ May 27 2005, 01:22 PM)
YIC - Don't you mean 1.204x10^24 atoms?

Tupac - It's 0.5 moles of molecules but 1 mole of atoms and therefore 1 mole of electrons, right?

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Yeah that is right sorry, it was a typo biggrin.gif

I had read over my notes and I saw that 1 mol of hydrogen was L molecules (not L atoms) meaning 2L atoms so a half mole is L atoms which is L electrons





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