## 4.15 Homework help

DHavo_1E
Posts: 118
Joined: Sat Aug 17, 2019 12:17 am

### 4.15 Homework help

Hello,

Could anyone explain how they solved this problem? I am a bit confused on the solution manual's approach regarding their usage of enthalpy of reaction and why the specific heat capacity is negative in the heat equation q=mcdeltaT as well as where they got 800g. Thank you so much!

The problem is: Hydrochloric acid oxidizes zing metal in a reaction that produces hydrogen gas and chloride ions. A piece of zinc metal of mass 8.5g is dropped into an apparatus containing 800.0mL or 0.500M HCl(aq). If the initial temperature of the hydrochloric acid solution is 25C, what is the final temperature of this solution? Assume that the density and molar heat capacity of the hydrochloric acid solution are the same as those of water and that all the heat is used to raise the temperature of the solution.
Last edited by DHavo_1E on Tue Feb 11, 2020 9:48 pm, edited 1 time in total.

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### Re: 4.15 Homework help

Ruby Richter 2L
Posts: 103
Joined: Thu Jul 25, 2019 12:17 am

### Re: 4.15 Homework help

Ruby Richter 2L
Posts: 103
Joined: Thu Jul 25, 2019 12:17 am

### Re: 4.15 Homework help

Ok figured it out. Since you are looking at the change in temperature of the solution, you need to use its mass, not the mass of zinc (8.5g). The question tells you that the density of the hydrochloric acid solution is the same as that of water, which is 1g/1ml. Since there are 800ml HCl, mass is therefore 800g.

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