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# Enthalpy change. Watch

1. If i add 2g of KHCO3 to 30cm^3 of 1gcm^-3 solution.

when i work out the enthalpy change from mass of solution x 4.18 x Temperature change.

Is the mass of solution 32 or 30 g. If it was mass of mixture is would be 32 but i dont know if KHCO3 dissolves and therefore should be counted as part of the solution.

Thanks alot
2. (Original post by Goods)
If i add 2g of KHCO3 to 30cm^3 of 1gcm^-3 solution.

when i work out the enthalpy change from mass of solution x 4.18 x Temperature change.

Is the mass of solution 32 or 30 g. If it was mass of mixture is would be 32 but i dont know if KHCO3 dissolves and therefore should be counted as part of the solution.

Thanks alot
can you add 2 g and 30 cm cube together? (think of whether you can 1 apple and 1 orange together)
3. (Original post by shengoc)
can you add 2 g and 30 cm cube together? (think of whether you can 1 apple and 1 orange together)
I gave the mass per unit volume if you read my question.
4. 1g = 1cm^3 so you can actually add them two values together. You'd use 30 though. You'd only use the 2g when you're figuring out how many moles of KHCO3 reacted
5. (Original post by Goods)
I gave the mass per unit volume if you read my question.
true, but what i was trying to imply was that you can't make sense of adding the two up with their current units unless you convert one of them based on the density information.

i.e. apple is a fruit, orange is a fruit. i have two kinds of fruits there. i have just "added" them up based on a common feature.

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Updated: April 12, 2013
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