Question

What is the mass percentage of carbon in 5.000 G of sucrose

Answer 1

Answer : The mass percentage of carbon in sucrose  is, 42.1 %

Explanation: Given,

Molar mass of C = 12 g/mole

Molar mass of H = 1 g/mole

Molar mass of O = 16 g/mole

First we have to calculate the molar mass of sucrose.

Molar mass of sucrose $(C_{12}H_{22}O_{11})$ = $12(12)+22(1)+11(16)=342g/mole$

Now we have to calculate the mass of carbon in 5 g of sucrose.

As we now that there are 12 number of carbon atoms, 22 number of hydrogen atoms and 11 number of oxygen atoms.

The mass of carbon = $12\times 12=144g$

As, 342 g of sucrose contains 144 g of carbon

So, 5 g of sucrose contains $\frac{5}{342}\times 144=2.105g$ of carbon

Now we have to calculate the mass percentage of carbon in sucrose.

Formula used :

$\%\text{ Mass percentage of carbon}=\frac{\text{Mass of carbon}}{\text{Mass of sucrose}}\times 100$

Now put all the given values in this formula, we get:

$\%\text{ Mass percentage of carbon}=\frac{2.105}{5}\times 100=42.1\%$

Therefore, the mass percentage of carbon in sucrose  is, 42.1 %

Answer 2

17) 8.4 / 20 x 100

18) 20 . 0.5150

19) 6,50% because (as you said) the law of definite proportions states that regardless of the amount, a compound is always composed of the same elements in the same proportion by mass