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# AS chemistry help? Watch

1. How would you approach this question?

Which of the following contains the most chloride ions?[1 mark]
A 10 cm3 of 3.30 × 10–2 mol dm–3 aluminium chloride solution
B 20 cm3 of 5.00 × 10–2 mol dm–3 calcium chloride solution
C 30 cm3 of 3.30 × 10–2 mol dm–3 hydrochloric acid
D 40 cm3 of 2.50 × 10–2 mol dm–3 sodium chloride solution
2. A) Aluminium Chloride solution: AlCl3
(10*3.3)/1000=0.033
B) Calcium Chloride solution: CaCl2
(20*5)/1000=0.100
C) Hydrochloric acid: HCl
(30*3.3)/1000=0.099
D) Sodium Chloride solution: NaCl
(40*2.5)/1000=0.100

From what i can see it's going to be either CaCl2 or NaCl, and I kind of confused myself :/
3. (Original post by Libaan)
A) Aluminium Chloride solution: AlCl3
(10*3.3)/1000=0.033
B) Calcium Chloride solution: CaCl2
(20*5)/1000=0.100
C) Hydrochloric acid: HCl
(30*3.3)/1000=0.099
D) Sodium Chloride solution: NaCl
(40*2.5)/1000=0.100

From what i can see it's going to be either CaCl2 or NaCl, and I kind of confused myself :/
Almost there!
Firstly, you just need to divide each one by 100, because the concentration is ___ x 10-2 moldm-3

Then, just realise that, for example

AlCl3 ---> Al3+ + 3Cl-

So if you have 0.00033 mol of AlCl3 you're gonna end up with
0.00033 x 3 = 0.00099 mol of Cl-

Apply the same amount of reasoning to the other solutions and you'll find that CaCl2 has the highest amount of Chloride Ions

You're not the OP I know, but it'll help both of you.
4. Thank you so much guys for your help

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