>>> Which of the following contains 1 mole of the
stated particles?
A Electrons in 1g of hydrogen gas
B Ions in 100g of calcium carbonate
D Oxygen atoms in 1 mole of oxygen gas ( i know it's obviously
wrong but is there any way to prove that it's wrong? i mean, how do
i present workings to validate my claim?)
Answer being A, I chose B. Why is it that the reference
to 'electrons' is accepted? For option B, am I wrong
because CaCO3 is insoluble and thus cannot dissociate into ions? (I
think it's this case, hahaha) <<<
B is wrong because you only considered moles of the ionic
compound, not moles of ions within the compound. You have to
consider both cations and anions. Just because CaCO3 is insoluble
in water does not mean cations and anions are not present. Just
because you can't separate your hands from your body does not mean
they are not present and that you needn't count them.
There are two moles of O atoms per mole of O2 molecules.
>>> Which statement(s) about a 12.0g sample of
12C are correct?
There is this statement which I marked as 'correct' when in fact
it is wrong...
"The no. of atoms is the same as the number of atoms in 2.0g of
1 H2..." (1 is written as a top subscript)
I mean the no. of moles of H atoms will be = 2.0 /
(1+1)
=1 mol
So isn't no. of moles = 1 X 6.02 X 10^23, same as that of 12.0g
sample of 12C? <<<
No. of atoms in 12g sample of C = 1 mol of atoms
No. of atoms in 2g of H2 = 1 mol of H2 molecules = 2 mol of
H atoms (since 1 mole of H2 molecules contain 2 moles of H
atoms)
>>> How many moles of fluoride ions are there in 20g of
aluminium fluoride?
my workings: no of moles of AlF3 = 20 / (19 X 3 + 27) = 0.238095
mol
so no. of fluoride ions = 0.238095 X (3/4) = 0.179 mol (3
s.f) <<<
No. of F- ions = no. of mol of AlF3 x 3 = 0.238095 x 3 =
0.714 mol