## Calculating the Net Change in Moles of a Gas to find Delta V

$\Delta U=q+w$

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Shelby_Smallwood_2B
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Joined: Fri Sep 26, 2014 2:02 pm

### Calculating the Net Change in Moles of a Gas to find Delta V

In homework 7.51, you need to calculate the change in volume using the ideal gas law. In order to do that, you must calculate the net change in gas moles (The balanced equation is given). How do you calculate the net change in the moles of gases in the reaction?

Niharika Reddy 1D
Posts: 127
Joined: Fri Sep 26, 2014 2:02 pm

### Re: Calculating the Net Change in Moles of a Gas to find Del

Net change in moles of gas=Δn=(moles of gas in the products)-(moles of gas in the reactants)

For this problem, there are 3 moles of gas in the products and 2 moles of gas in the reactants, so the net change in moles of gas is 3-2=1 mol.

Shelby_Smallwood_2B
Posts: 3
Joined: Fri Sep 26, 2014 2:02 pm

### Re: Calculating the Net Change in Moles of a Gas to find Del

Thanks so much. Is it possible to have a negative net change in moles or would you do the absolute value?

Neil DSilva 1L
Posts: 70
Joined: Fri Sep 26, 2014 2:02 pm

### Re: Calculating the Net Change in Moles of a Gas to find Del

You can have a negative$\Delta$ values. It follows the same sorta thinking as $\Delta H$ or $\Delta V$. It just means the change was a negative change and the final value is less than the initial value. So, for example, if there are 4 moles of gas in the reactants (instead of 2), $\Delta n = -1$.

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