Question

How many moles of nitrogen are in a 14.57 gram sample of nitrogen?

Answer 1

`\boxed {\boxed {\sf About \ 1.040 \ moles \ of \ nitrogen }}`

Step-by-step explanation:

To convert from grams to moles, we must use the molar mass. This can be found on the Periodic Table. We have a sample of nitrogen, so look for N on the table.

• Nitrogen (N): 14.007 g/mol

Now, use this molar mass as a ratio.

`\frac {14.007 \ g \ N }{1 \ mol \ N }`

Multiply by the number of grams in the sample (14.57)

`14.57 \ g \ N *\frac {14.007 \ g \ N }{1 \ mol \ N }`

Flip the fraction so the grams of nitrogen will cancel.

`14.57 \ g \ N *\frac {1 \ mol \ N }{14.007 \ g \ N}`

`14.57 *\frac {1 \ mol \ N }{14.007 }`

`\frac {14.57 \ mol \ N }{14.007 }`

`1.04019419 \ mol \ N \\`

The original measurement of grams had 4 significant figures, so we need to round our answer to the same number of sig figs.

For the number we calculated, that is the thousandth place. The 1 in the ten thousandth place tells us to keep the 0 in the thousandth place.

`1.040 \ mol \ N`

There are about 1.040 moles of nitrogen in 14.57 grams.