Question

Calculate molecular weight of pantothenic acid vitamin B5 C6H17NO5? 2) the recommend Daly allowance of niacin 15 mg. How many moleculars of vitamin B3 does the government recommend that you ingest every day?

Answer 1

The molar mass of pantothenic acid is `219.24 "g/mol"`.
The number of vitamin B3 molecules in `15mg` is `7.2 *10^19`.

Explanation:

1: Molecular Weight of Panthothenic Acid

Because you said pantothenic acid and vitamin B5, I think you meant `C_9H_17NO_5` instead of `C_6H_17NO_5`.

The molar mass of `C_9H_17NO_5` is the sum of the atomic masses:

`9*C + 17*H + N + 5*O = 9*12.01 + 17*1.008 + 14.01 + 5*16.00 = 219.24 "g/mol"`

2: Molecules of Vitamin B3
Vitamin B3, or niacin, has the formula `C_6H_5NO_2`. The mass of one mole of vitamin B3, or its molar mass, is:

`6*C + 5*H + N + 2*O = 6*12.01 + 5*1.008 + 14.01 + 2*16.00 = 123.11 "g/mol"`

For every `123.11g`, there is `1` mole of niacin.
`"15mg"` is the same as `"0.015g"`. The number of moles in `"0.015g"` is:

`0.015/123.11 = 0.00012`.

One mole represents `6.022*10^23` of something, so `0.00012` moles of niacin represents `0.00012 * 6.022*10^23 = 7.2 *10^19` molecules. :)