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Topic: thermochemistry  (Read 2293 times)

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Offline NarrowRaptor715

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thermochemistry
« on: September 30, 2018, 06:11:58 PM »
When 10.00 mL of a solution of strong acid is mixed with 100.00 mL of a solution of weak base in a coffee-cup calorimeter, the temperature rises from 22.0 oC to 26.7 oC. Determine q for the acid-base reaction, assuming that the liquids have densities of 1.00 g/mL and the same heat capacities as pure water.

So I tried adding the solutions and then using the equation q=mc deltaT to be the q value but I was told I was getting the wrong answer and was unable to find the correct answer anywhere after contacting friends.

If you can tell me where i got the answer wrong please let me know.

Offline Borek

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Re: thermochemistry
« Reply #1 on: September 30, 2018, 06:49:18 PM »
If you can tell me where i got the answer wrong please let me know.

You didn't give us a chance - you have not posted enough information. We have no idea what you have calculated, how you did it, and what was the result you got.

Actually it is not even clear what is the question, as

q for the acid-base reaction

is quite ambiguous.
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Offline NarrowRaptor715

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Re: thermochemistry
« Reply #2 on: September 30, 2018, 07:05:56 PM »
My apologies

It asks us to find q of the acid base reaction because it says determine q for the acid base reaction so thats self explanatory my apologies for not making that clearer.

I added the ml of the solutions to get 120 ml and since density is 1g/ml it would be 120 g which would be the mass
the specific heat capacity is 4.19 cus its water and it states it in the question.
The change in temp is 26.7-22 which would be 4.7

I plugged this into the equation q= mc deltaT and i got 2363.16 joules
when this was inputted into an electronic system it told me the answer was wrong and that made me really confused and motivated to achieve the right answer so I consulted this forum to help.

Is this sufficient information?
I am clearly new, i just made the account today and did not know how to generally go about things so I apologize for my wrong doing.


Offline Borek

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Re: thermochemistry
« Reply #3 on: October 01, 2018, 02:52:51 AM »
It asks us to find q of the acid base reaction because it says determine q for the acid base reaction so thats self explanatory

Actually no, that's still not unambiguous (which can be source of your problems).

Quote
I added the ml of the solutions to get 120 ml and since density is 1g/ml it would be 120 g which would be the mass
the specific heat capacity is 4.19 cus its water and it states it in the question.
The change in temp is 26.7-22 which would be 4.7

I plugged this into the equation q= mc deltaT and i got 2363.16 joules

Haven't checked the numbers but the logic looks OK (although the sign might be off, do you know the convention of what negative q means?).

Quote
when this was inputted into an electronic system it told me the answer was wrong

Well, you calculated amount of heat that was released in this particular case. That's not necessarily the same as "q for the acid base reaction".

Have you listed all given information, or have you omitted some?
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Offline mjc123

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Re: thermochemistry
« Reply #4 on: October 01, 2018, 04:58:08 AM »
10 mL + 100 mL is not 120 mL.

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