## Sig Fig Rules (Hess's Law)

Soonwoo Chung 1D
Posts: 26
Joined: Wed Sep 21, 2016 2:57 pm

### Sig Fig Rules (Hess's Law)

When using Hess's Law, we add the enthalpies at the end, so do we use the sig fig rule in which we use the lowest amount of decimals even if we had to multiply the separate enthalpies to even out the equation?

Christine_Mavilian_3E
Posts: 30
Joined: Fri Jul 22, 2016 3:00 am

### Re: Sig Fig Rules (Hess's Law)

Regardless of whether you are flipping the equation and/or multiplying and dividing numbers to get your "desired" reaction, the significant figures in your final answer ( which would be the sum of your enthalpies) would depend on the lowest number of decimal places in the values you are adding/subtracting.

I hope this helps!

samuelkharpatin2b
Posts: 55
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Sig Fig Rules (Hess's Law)

When using Hess's Law, your final answer would depend on the smallest number of decimal places in your enthalpies for sure. The reason why is because adding/subtracting is the last step you do in order to obtain your final answer. And since adding/subtracting is your final step in calculating the enthalpy of reaction, you must obey the adding/subtracting sigfig law.

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