# Heat of reaction

#### msdel

I conducted an expereiment where I added 5.5g of NaOH into 200ml of 1.0 mol/l of HCl. Ive done all the calculations required but there is a questoin im just not sure about. It asked if i was to add 11.0g of NaOH instead of the 5.5g i used would this have an effect on the amount of heat evolved? I was thinking that the heat evolved would stay the same...

Can anyone help me understand this one?

Thanks

#### gravenewworld

Look up the heat of formation data for HCL and NaOH. If the sum of those two is negative then the enthalpy of the reaction will decrease if you use twice as much NaOH since the enthaply of a reaction is directly related to the amount of starting material you use. If the sum of those two is positive then the enthalpy of the reaction will increase.

Last edited:

#### LeonhardEuler

Gold Member
Since NaOH has a mol. wt. of 40g/mol, 5.5g of it is only about .14 mol. You used .2 mol of HCl, so adding more NaOH would cause a further reaction. This would increase the heat evolved.

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