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How many hydrogen atoms are contained in 8.66 moles of $\ce{NH3}$? The answer is given after the log has been taken, so the final answer is 25.19.

What I have been doing is multiplying $8.66\text{ by }6.02\times10^{23}=5.21332\times10^{24}$ and when I take the log of that I get 24.71. I'm not sure what to do to get the correct answer.

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Before you use log you have to multiply the answer of $8.66~\mathrm{mol}$ by $6.02 \cdot 10^{23}$ by 3 because the answer of $8.66~\mathrm{mol}$ by $6.02 \cdot 10^{23}$ gives you the number of ammonia molecules and in each molecules there are 3 hydrogen atoms present.

So it is:

$$8.66 \cdot 6.02 \cdot 10^{23} = 5.21332 \cdot 10^{24}$$

$$5.21332 \cdot 10^{24} \cdot 3 = 1.563996 \cdot 10^{25}$$

$$\log(1.563996 \cdot 10^{25}) = 25.19$$

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