Can someone asnwer this for me and show me How Really stuck

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girlslovebarbie
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Revise this neutralisation reaction:


2 H3PO4(aq) + 3 Ca(OH)2 (aq) → Ca3(PO4)2 + 6 H2O



work out the volume of 0.75 M H3PO4 necessary to neutralise 35 ml of 0.45 M Ca(OH)2

Breakdown of how I do this would greatly help
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EierVonSatan
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Welcome to TSR. The rules of the study forums forbid giving you a full worked answer to the problem.

What you need to do for this problem, though, is to first find out how many moles of calcium hydroxide there are. Next, you can use the chemical equation to work out how many moles of acid you need (the stoichiometric ratio). Finally, knowing the moles and concentration of the acid, you have to find the volume. Give it a go and we'll help you if you run into any problems :yy:

(I will PM you TheGameOfScience :p:)
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TheGameOfScience
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(Original post by EierVonSatan)
Welcome to TSR. The rules of the study forums forbid giving you a full worked answer to the problem.

What you need to do for this problem, though, is to first find out how many moles of calcium hydroxide there are. Next, you can use the chemical equation to work out how many moles of acid you need (the stoichiometric ratio). Finally, knowing the moles and concentration of the acid, you have to find the volume. Give it a go and we'll help you if you run into any problems :yy:
yes!!!! i finally found you!! i need your urgent help and expertise on chemistry! how should i revise for a2 aqa chemistry? should i just purely do exam questions using my notes to help me when i cant figure out the question? some people told me to do this and it did ork for me but some other people also said dont do it, only do past papers without notes when you know content, also i dont want to waste my past exam papers as i dont have regular access to a printer. or should i just create mindmaps/flashcards, how did you revise for chem and whats the best way you think i should revise for chem? and could someone pass chemistry by just doing as many past paper questions as possible?
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Plantagenet Crown
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(Original post by girlslovebarbie)
Revise this neutralisation reaction:


2 H3PO4(aq) + 3 Ca(OH)2 (aq) → Ca3(PO4)2 + 6 H2O



work out the volume of 0.75 M H3PO4 necessary to neutralise 35 ml of 0.45 M Ca(OH)2

Breakdown of how I do this would greatly help
1. You've been given the volume and concentration of Ca(OH)2. So first work out the mols of calcium hydroxide by multiplying these 2 values together. (Don't forget to convert ml to dm3 first).

2. Now as the ratio of Ca(OH)2 to H3PO4 is 3:2, whatever answer you get to part 1, you multiply by 2/3.

3. This number is now the moles of H3PO4​. To get the concentration you divide this number by 0.75 as conc = moles/vol
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girlslovebarbie
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so would it be 0.035 x 0.45 = 0.01575 x 2 = 0.0315/3 = 0.0105/0.75

= 0.014

Am i correct
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EierVonSatan
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(Original post by girlslovebarbie)
so would it be 0.035 x 0.45 = 0.01575 x 2 = 0.0315/3 = 0.0105/0.75

= 0.014

Am i correct
Yeah 0.014 dm3 :yy:
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Plantagenet Crown
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(Original post by girlslovebarbie)
so would it be 0.035 x 0.45 = 0.01575 x 2 = 0.0315/3 = 0.0105/0.75

= 0.014

Am i correct
Yes
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Borek
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(Original post by girlslovebarbie)
0.035 x 0.45 = 0.01575 x 2 = 0.0315/3 = 0.0105/0.75

(...)

Am i correct
While the answer you got is correct, the way you wrote the solution is horrendous :eek:

0.035 x 0.45 = 0.01575
0.01575 x 2 = 0.3034
0.0315/3 = 0.105
0.0105/0.75 = 0.014

so

0.035 x 0.45 ≠ 0.01575 x 2 ≠ 0.0315/3 ≠ 0.0105/0.75
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