Question

How many kilograms of chlorine are in 21 kg of CF2Cl2

Answer 1

Answer : The mass of chlorine present in sample is 12.32 kilograms.

Explanation :  Given,

Mass of $CF_2Cl_2$ = 21 kg = 21000 g     (1 kg = 1000 g)

First we have to calculate the moles of $CF_2Cl_2$.

Molar mass of $CF_2Cl_2$ = 121 g/mole

$\text{ Moles of }CF_2Cl_2=\frac{\text{ Mass of }CF_2Cl_2}{\text{ Molar mass of }CF_2Cl_2}=\frac{21000g}{121g/mole}=173.5moles$

Now we have to calculate the moles of chlorine.

In the molecule $CF_2Cl_2$, there are 1 mole of carbon, 2 moles of fluorine and 2 moles of chlorine.

As, 1 mole of $CF_2Cl_2$ contains 2 moles of chlorine

So, 173.5 moles of $CF_2Cl_2$ contains $173.5\times 2=347$ moles of chlorine

Now we have to calculate the mass of chlorine.

$\text{ Mass of chlorine}=\text{ Moles of chlorine}\times \text{ Molar mass of chlorine}$

Molar mass of chlorine = 35.5 g/mole

$\text{ Mass of chlorine}=(347moles)\times (35.5g/mole)=12318.5g=12.32kg$

Therefore, the mass of chlorine present in sample is 12.32 kilograms.

Answer 2

21 kg x [(3 x 35.45)/(12.01 + 19.00 + (3 x 35.45))] =  

21 kg x (106.35/137.36) = 16.3 kg of chlorine  

You just multiply the weight of the material by the fraction of chlorine (by weight). The others are done the same way