Im a titration 25cm3 of ammonia (NH3) solution with 33 cm3 of 2.26g/dm3 HCl. What is the concentration of the ammonia solution? NH3 + HCl --> NH4Cl

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hey can someone please explain how to calculate this titration question :) ??

GCSE chemistry C7

Posted Wed 23rd May, 2012 @ 19:04 by 94Y86

24 Answers

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Okay first work out the relative formula masses of the reactants.

Secondly divide 2.26 by 1000 then times this by 33cm(3).

Next divide the 25cm by 33cm, times this by what you got from the last equation.

Finally times the amount from the last equation by 1000 divided by 25

This will give you the g/dm3 of the nitric acid

Answered Wed 23rd May, 2012 @ 19:20 by Georgia Sowden
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Ok- this isn't the method that everyone uses but my chemistry teacher showed me this way an it worked for me!
Start out by finding out how many moles of HCl you have (you'll see why in a sec) to find the moles you do volume x concentration divided by 1000. So this is 33 x 2.26 1000. This gives 0.075 moles to 2 dp. Find the ratio of HCl to NH3 by looking at the equation. In this case it is 1:1. That means you have 0.075 moles of NH3 as well.
To find the concentration of NH3 you can use the equation
'concentration = moles x 1000 divided by volume. This is 0.075 x 1000 / 25. This gives you 3 mol/dm3- this is a whole number because mole value has been rounded to 2 dp.. Hope this is useful :)

Answered Wed 23rd May, 2012 @ 19:21 by AmyPond
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u cant times 2.26 with 33 because 2.26 is in g/dm3 and 33 in cm3...they have to both cm3 or dm3! otherwise the calculation is just wrong!

Answered Wed 23rd May, 2012 @ 20:02 by Namita
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(volume x concentration of acid)/number of moles = (volume x concentration of alkali)/number of moles

That's how I was taught it last year when I did it.

So, (33 x 2.26)/1 = (25 x ???)/1

All you have to do, is work out what 33 x 2.26 is, and then divide that answer by 25 to work out the missing concentration.

Questions where you have 2 or more moles of one of the substances is harder and harder to explain, but if you look inside your notes from school and from revision guides, they'll be able to explain that step better than I can.

Hope I helped :)

[Edit] For clarification and comparison, the answer I got using this method was 2.98 (2dp)
This method only works for GCSE, as at A-level they want you to show the more long winded way of working it out. 

Answered Wed 23rd May, 2012 @ 19:16 by Hollie
Edited by Hollie on Wed 23rd May, 2012 @ 21:28
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thanks so much :) !!!

Answered Wed 23rd May, 2012 @ 19:20 by 94Y86
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haha :) thanks anyway, it was really useful i actually get it now :) thanks everyone!!!

Answered Wed 23rd May, 2012 @ 19:25 by 94Y86
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Y...my dad and I went through this question...and he got the same answer as me...so i give up and I am sticking to my method...as in the one I was taught by my chemistry teacher...and i honestly dont get how you got 2.9...whatever?? we even checked google! i mean google didnt have the same question...but it had methods that i followed and got the same answer from...

where did u get this question from??? CGP workbook??

Answered Wed 23rd May, 2012 @ 20:00 by Namita
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I got confused at cm3 and dm3 too at first when i was taught it- but i sorta got used to doing it that way and it makes sense after a while:):) to change them into the same unit I divided by 1000 - which is how I changed it in my answer to get them the same:) the way my chem teacher showed me looks really confusing but was the only way he could get me to understand!!

Answered Wed 23rd May, 2012 @ 21:26 by AmyPond
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Lucia...i can see how u got it...it was one of the other people who have answered who have kept cm3 and dm3 in the same calculation....and it doesnt make sense... -she says sheepishly-

i usually love chemistry calculations...but god..i hate it when the answer i get is different to the given answer >.< thats just the question being difficult >.<

Answered Wed 23rd May, 2012 @ 21:28 by Namita
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Ah sorry:) -says just as sheepishly- and me too- it confuses me so much! I've finished chemistry now though (im wjec) and so relieved! But I have physics tomorrow and the calculations are equally as irritating! I usually like Maths but science-y Maths is so confusing!

Answered Wed 23rd May, 2012 @ 21:38 by AmyPond
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sciency maths do tend to be more complicated...but i still like them (as long my answer is correct) :p

r u in year 11 as well then?? i am in year 11...we (Y and I) are doing OCR 21st century...and well...our chemistry is tomorrow...physics is sometime next week...

oh...and before i forget...GOODLUCK for your exam...physics and all the others u may have xD

Answered Wed 23rd May, 2012 @ 21:43 by Namita
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sciency maths do tend to be more complicated...but i still like them (as long my answer is correct) :p

r u in year 11 as well then?? i am in year 11...we (Y and I) are doing OCR 21st century...and well...our chemistry is tomorrow...physics is sometime next week...

oh...and before i forget...GOODLUCK for your exam...physics and all the others u may have xD

Answered Wed 23rd May, 2012 @ 21:43 by Namita
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Yeah I'm in year 11 - it seems to have crept up on me! It feels like i was in year 7 only yesterday! I'm WJEC- which seems to be giving me pretty ok questions so far... And yes, good luck to you too! I hope your chem questions are ok!!:):) science Maths is stressful for me which is ironic as I'm doing Maths physics and further Maths at a level and additional Maths level 2 sometime next month! Its ok when I get my head around it but for some reason this takes a LONG time! I only completely understood the moles question an hour before my exam- which was good because it came up!:)

Answered Wed 23rd May, 2012 @ 21:48 by AmyPond
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I didn't mean to cause any confusion! 

This is the method my chemistry teacher taught me at GCSE last year and I got an A* in the subject.

I found it so easy to understand, but perhaps that isn't the universal case.

I'd be happy to try and break it down for you so that you can understand it, but I don't want to confuse you any more.

Answered Wed 23rd May, 2012 @ 21:49 by Hollie
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oh my god...i totally get what u mean! year 7 was sooo good and i remember thinking year 11s are soo big and everything...

wow...thats a lot of maths for the next few years for u..what do u want to be then???

i am planning on taking biology, chemistry, maths (statistics) and geography next year :D

the titration questions always come up..and they phrase it soooo weirdly...you need half the time decphering the questions! anyway...lets hope for the best for tomorrow and for all the other exams left to come xD

how many exams do u have??

Answered Wed 23rd May, 2012 @ 21:51 by Namita
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Haha - yeah I thought they were big too (not that I'm big now- in only five foot two!) but I have no idea what I want to do:) I'm doing English as well as that is oddly my fave subject (which is ironic as I'm doing so many Maths based subjects and their completely different!)
And I know- the questions don't help us in any way! I litey have to sit there deciphering what they actually want me to answer before I can even get started on the calculation! I have about 14 exams for 13 subjects (because I did modules last summer and jan) so its not so bad:) how about you?

Answered Wed 23rd May, 2012 @ 22:02 by AmyPond
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hey...i am like 5 feet 2 as well!! :D hi 5!

wow...english and maths...thats an odd match...but as long as u like it...its all good :D english language or english literature? :?

the examiners are like set on making us lose marks...they probably just sit there laughing at our stupidity :/

i have 13 exams in total...i have done 5 already...so its not too bad...i have 2 tomorrow...chemistry and english lit poetry :/ but it will be fine...i am giving it the best i have...so :) we had modules as well like last jan, summer and again year 11 jan :D its helped me soo much...i mean i know people who have like 25+ exams now cause they didnt do modules...can u imagine that?? wow 8|

Answered Wed 23rd May, 2012 @ 22:08 by Namita
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Yay! Its not too bad being this height but the amount of comments I got on my leavers t-shirt about it was unreal;)Our school does Lang/lit so a mix of both which is awesome:£ yeah I have physics and lit (questions on a book and a play) which everyone in my year is dreading! But I'm consoling myself with the fact that in 24 hours I'll be sat here discussing how it was an it will all be over:)

Answered Wed 23rd May, 2012 @ 22:18 by AmyPond
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thats a good way of thinking about it :) after everyday i am enjoying saying have one less exam to do and i free ;) everyone has their own way of looking at the exam season in a positive way! :p

our height isnt too bad...but i do what a few more inches.. -she says sheepishly- :p

Answered Wed 23rd May, 2012 @ 22:19 by Namita
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Yes -I'm looking forward to the summer! The only downer is that all my friends have their last exam on the 19th of June and I have my last (additional Maths) on the 25th so I'll miss the celebrations for revising - trust me Ill need a solid week - the work is insanely difficult !! But itll preapare me for a level so... And the only bad thing about this height I've found is that you can't reach things off top shelves! And everyone thinks I'm about 12;) but better get some sleep! Good luck!:)

Answered Wed 23rd May, 2012 @ 22:29 by AmyPond
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ha ha...my last exam is on the 18th of june :p

but yeah...better get some sleep...talk to u some other time :p goodluck :D

Answered Wed 23rd May, 2012 @ 22:39 by Namita
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Good luck to you too:) yeah talk some other time- its interesting getting to know other people from other places going through the same thing!:)- especially when their my height!:)

Answered Wed 23rd May, 2012 @ 22:40 by AmyPond
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i completely get you! i love meeting new people...who r very like me :p

he he...we have to talk again...and we shall :D maybe tomorrow about how the exams went xD

GOODLUCK!!!!!!!!!! :D

Answered Wed 23rd May, 2012 @ 22:52 by Namita
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May the odds- you probably won't see this now- but how were your recent exams?:)

Answered Sat 26th May, 2012 @ 18:07 by AmyPond