# What’s the mass percent of each element in Penicillin G (C16H18N2O4S)???

## I’m kinda confused on this one aspect of chemistry and how to exactly get the answer.

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zhirou Share
Feb 11, 2018

Carbon: 57.47%
Hydrogen: 5.43%
Nitrogen: 8.38%
Oxygen: 19.14%
Sulfur: 9.59%

#### Explanation:

The mass percent of an element in a compound is basically this: Given any amount of a compound, what percentage of mass will that element take up?

We can find that using this formula:

$\text{Mass percent" = "Mass of element"/"Mass of compound}$

Let's say the amount of penicillin G is $1$ mole.
The mass of that would be:

${C}_{16} {H}_{18} {N}_{2} {O}_{4} S = 16 \times C + 18 \times H + 2 \times N + 4 \times O + S$
$\text{= 16} \times 12.01 + 18 \times 1.008 + 2 \times 14.01 + 4 \times 16.00 + 32.06$
$\text{= 334.384 g/mol}$

If there's $1$ mole of penicillin G, there must be $16$ moles of carbon because $C$ has a subscript of $16$ in ${C}_{16} {H}_{18} {N}_{2} {O}_{4} S$.

That means that the mass of carbon is:

$16 \times C = 16 \times 12.01 = 192.16$

With this, we can find the mass percent of carbon in penicillin G.

"Mass of element"/"Mass of compound" = 192.16 / 334.384 = 0.5747 = 57.47%

We can use the same method to figure out the mass percents of the other elements in penicillin G:

• Hydrogen is (18xx1.008) / 334.384 = 0.0543 = 5.43%.
• Nitrogen is (2xx14.01) / 334.384 = 0.0838 = 8.38%.
• Oxygen is (4xx16.00) / 334.384 = 0.1914 = 19.14%.
• Sulfur is (1xx32.06) / 334.384 = 0.0959 = 9.59%.

To confirm this, we can add these up; if our calculations were correct, they should add up to 100%.

57.47% + 5.43% + 8.38% + 19.14% + 9.59% = 100%

Yay! :)

Then teach the underlying concepts
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#### Explanation

Explain in detail...

#### Explanation:

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anor277 Share
Feb 11, 2018

Divide the mass of the element present by the molecular mass, and multiply this by one hundred percent....

#### Explanation:

We gots...${C}_{16} {H}_{18} {N}_{2} {O}_{4} S$, whose molecular mass is $334.39 \cdot g \cdot m o {l}^{-} 1$...

And so %C=(16xx12.011*g*mol^-1)/(334.39*g*mol^-1)xx100%=57.5%

%H, %N, %O, %S are...???

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