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chemistry a level acids

when a strong acid dissociates,

e.g. HCl --> H(+) + Cl(-)

is Cl(-) the conjugate base then?

does Cl(-) dissociate in equal proportions to H(+)?

how is [HA] = [H(+)], if Cl(-) does dissociate in equal proportions,
wouldn't [HA] / 2 = [H(+)} instead?
Reply 1
Avatar for dlsoii
dlsoii
13
Original post by hj!gz
when a strong acid dissociates,

e.g. HCl --> H(+) + Cl(-)

is Cl(-) the conjugate base then?

does Cl(-) dissociate in equal proportions to H(+)?

how is [HA] = [H(+)], if Cl(-) does dissociate in equal proportions,
wouldn't [HA] / 2 = [H(+)} instead?

No, you see, according to the balanced equation: 1 mol HCl -> 1 mol (H+) + 1 mol (Cl-). Therefore, for any solution of HCl, the molar quantity of HCl is equal to that of H+, and given that the volume of the solution is constant [H+] = [HCl] using concentration = mol/volume. Equally, if you knew [Cl-] , you could determine [HCl] as their molar quantities are also equal.
Reply 2
Avatar for hj!gz
hj!gz
OP
12
okay....
yeah, that makes sense, thank you!
Doing an access course - I understand how you get the mole/1000ml, but don't understand things like
"A glucose solution with a volume of 2.0L contains 72g glucose (C6,H12,O6). If glucose has a molar mass of 180g/mole, what is the molarity of the glucose solution?"

Can anyone help/explain please?
1 mole of glucose weighs 180 g
How many moles weigh 72 g?

Once you find the moles, use Concentration = moles / volume
Volume must be in dm3 or L

This will give you the answer. {Molarity is number of moles in one litre (so moles/volume)}
Original post by flowerscat
1 mole of glucose weighs 180 g
How many moles weigh 72 g?

Once you find the moles, use Concentration = moles / volume
Volume must be in dm3 or L

This will give you the answer. {Molarity is number of moles in one litre (so moles/volume)}

Ok, thanks. Does 0.20M sound right to u?
Original post by Amanda *M*
Ok, thanks. Does 0.20M sound right to u?

Yes, it does :smile:
Original post by flowerscat
Yes, it does :smile:

Sorry to bother you again. I worked it out by dividing 72 by 180. But don't really understand why I did that? It seems strange to divide 72 by 180?
You are not dividing 72 by 180. You divide 1 by 180, then multiply the answer by 72.

10 apples cost £50
How many apples can you buy for £8?

You would divide 10 by 50, to find the cost per apple, and then multiply the result by 8.

Same principle applies to your problem. Does this help?
How the hell is the rate found ?
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Original post by Amanda *M*
How the hell is the rate found ?


Check this excerpt out...
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