Question

addition of 1.280g of zinc metal to 100mL of 0.3917 M HCl in a coffee-cup calorimeter causes the temperature to increase from 1 degrees celsius to 22.11 degrees celsius. What is the value of the change of Hrxn for the following equation:
Zn(s) + 2HCl(aq)-->ZnCl2(aq) +H2(g)
Assume the density and specific heat of the solution are 1g/mL and 4.18J/g

So far I know that you must multiply: (1.28g)(22.11-15)(4.18)=

I don't know what to do after this step

Answer 1

I am trying to find Kj/mol in reaction

Answer 2

Did you make a typo? From your work I assume Ti is 15 and not 1 as you posted.
Your q calculation is almost correct. It should be 100 mL x 4.18 x (21.11-Ti) = q in Joules.

Note it's the water you're heating and although the Zn absorbs a little heat you're ignoring that. 100 mL H2O with a density of 1.0 g/mL = 100 grams.
So you have q for the reaction. That's q for 1.28g Zn. Then delta H = q/1.28 x (atomic mass Zn/1 mol) = J/mol. Convert that to kJ/mol.

Answer 3

So I did: 100 x 4.18 x (21.11-15)=2553.98 then I divided it by 1.28=1995.29
and I multiply it by 65.28/1mol=12969. Divide it by 1000 to get 130kJ/mol but its still not the right answer =(

Answer 4

The problem says 22.11 and not 21.11 (and I made the same typo in my response) and atomic mass Zn is 65.38 and not 65.28.

Answer 5

Yes okay thank you! I figured it out.