The Student Room Group

Chemistry unit 3 ial

Can anyone help me with number (v)?
Why aren’t we multiplying it by 4 instead of 2? Half the volume is used and double the concentration. So shouldn’t the temp change be multiplied by 4?
Reply 1
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what is changing is the moles

before, the no of moles was 1* (50 divided by 1000)= 0.05 mol


now, the no of moles is 2* (25 divided by 1000)= 0.05 mol


actually the temp shouldnt change at all, cuz the same no of moles are reacting
so the same no of molecules are reacting
Reply 3
Markscheme says 5.5x2=11
If you lit a fire in a small room, would you expect that the same fire would heat a room twice the size to the same average temperature?
The energy change would be the same, but you are heating up a smaller mass of liquid.

Ξ”E = mcΞ”T

If Ξ”E, and c are constant

Then Ξ”T is inversely proportional to m

i.e. if the mass halves, the temperature doubles
Anyone done
Reply 8
Yea
Ok lets
Discuss
Ok
What was the answer for the very last question about calculating mass?
And why do we add sodium chloride?
It was 0.107 but i thinkit's wrong😯
I got 16.8g
Will they give ecf mark if someone determines the wrong temperature rise ?

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