Chemistry OCR MCQ Negative Enthalpy? (Entropy Change Question) [PLEASE HELP]

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nwmyname
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#1
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#1
I have a question from OCR Chemistry A-level attached.

I know instantly that C and D are wrong, leaving A and B.

The answer is A, but I'm confused why the enthalpy change is negative, not positive.
Can someone please explain why the enthalpy change is negative?
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h3rmit
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#2
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#2
(Original post by nwmyname)
I have a question from OCR Chemistry A-level attached.

I know instantly that C and D are wrong, leaving A and B.

The answer is A, but I'm confused why the enthalpy change is negative, not positive.
Can someone please explain why the enthalpy change is negative?
Acid base neutralisations are exothermic, generally.
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Pigster
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(Original post by h3rmit)
Acid base neutralisations are exothermic, generally.
CaCO3 isn't a base.
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h3rmit
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(Original post by Pigster)
CaCO3 isn't a base.
Not technically, but it acts as a base in OP's reaction.
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Ze Witcher
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#5
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(Original post by nwmyname)
I have a question from OCR Chemistry A-level attached.

I know instantly that C and D are wrong, leaving A and B.

The answer is A, but I'm confused why the enthalpy change is negative, not positive.
Can someone please explain why the enthalpy change is negative?
The reaction is exothermic as bonds are being formed.
CaCl2 is formed in the process, as well as CO2 and H2O.

The reaction has a positive entropy change as the system is becoming more disordered; going from a solid state to a liquid/aq/g state on the right hand side.
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Pigster
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#6
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(Original post by nwmyname)
I have a question from OCR Chemistry A-level
Is that OCR A or B (Salters)?
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username986184
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#7
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(Original post by Pigster)
CaCO3 isn't a base.
Please explain.
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Pigster
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#8
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#8
(Original post by TeachChemistry)
Please explain.
It is a salt of carbonic acid.

Is sodium hydrogencarbonate an acid? It can, afterall, donate a proton. Which surely makes it an acid. But it dissolved into water to make pHs greater than 7 (@ 25 oC).
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