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moles question helpppppp!!!!!

hiiiii

please help me im so stuck!! :frown:

calculate the number of moles of the chloride ion in 0.5g CaCl2

mr of CaCl2 =110

a)4.5 mol
b)0.9mol
c)0.009mol
d)0.0045mol

THANKSSSS :biggrin:

Reply 1

Petulia

n = m / Mr
moles = mass / molar mass
mass: 0.5
molar mass: 110
0.5 / 110 = 0.0045mol

Reply 2

maamm

Original post by Petulia

n = m / Mr
moles = mass / molar mass
mass: 0.5
molar mass: 110
0.5 / 110 = 0.0045mol

I thought this was how to do it too ..but the question says how many moles of the chloride ion :/

Reply 3

LadyEcliptic

Try multiplying it by 2 then seeing as there are 2 chloride ions? what is the actual answer?

Edit: It still looks like it's going to be 0.0045 because:

% of CL2 in CaCl2 = 71/110 = 65% = 0.325g

moles = 0.0325/71 = 0.0045

(edited 9 years ago)

Reply 4

alow

Original post by maamm

I thought this was how to do it too ..but the question says how many moles of the chloride ion :/

How many moles of chloride are there per mole of Calcium Chloride?

Reply 5

maamm

Original post by alow

How many moles of chloride are there per mole of Calcium Chloride?

Ummm 2 moles chloride to 1 mole calcium I think :-/

Reply 6

GDN

The Mr of CaCl2 is 111.1 so the number of moles of CaCl2 is 0.5/111.1

= 0.00450 (to 3 sig fig)

Remember the number of moles is just number - if you consider 10 water molecules you have 10 oxygen atoms and 20 H atoms. Apply the same logic to your CaCl2