Question

Determine the number of moles of compound and the number of moles of each type of atom in each of the following:

Answer 1

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$     .....(1)

• For a:

Mass of propylene = 25 g

Molar mass of propylene = 42 g/mol

Putting values in equation 1, we get:

$\text{Moles of }C_3H_8=\frac{25g}{42g/mol}=0.6mol$

In 1 mole of propylene, 3 moles of carbon atoms and 8 moles of hydrogen atoms are present.

So, in 0.6 moles of propylene, $(3\times 0.6)=1.8mol$ of carbon atoms and $(8\times 0.6)=4.8mol$ of hydrogen atoms are present.

Thus, the number of moles of compound is 0.6 moles and number of moles of carbon and hydrogen atoms are 1.8 moles and 4.8 moles respectively.

• For b:

Mass of glycine = $3.06\times 10^{-3}g$

Molar mass of glycine = 75 g/mol

Putting values in equation 1, we get:

$\text{Moles of glycine}=\frac{3.06\times 10^{-3}g}{75g/mol}=4.08\times 10^{-5}mol$

In 1 mole of glycine, 2 moles of carbon atoms, 5 moles of hydrogen atoms, 1 mole of nitrogen atom and 2 moles of oxygen atoms are present.

So, in $4.08\times 10^{-5}mol$ of glycine, $(2\times 4.08\times 10^{-5})=8.16\times 10^{-5}mol$ of carbon atoms, $(5\times 4.08\times 10^{-5})=2.04\times 10^{-4}mol$ of hydrogen atoms, $(1\times 4.08\times 10^{-5})=4.08\times 10^{-5}mol$ of nitrogen atoms and $(2\times 4.08\times 10^{-5})=8.16\times 10^{-5}mol$ of oxygen atoms are present.

Thus, the number of moles of compound is $4.08\times 10^{-5}mol$ moles and number of moles of carbon, hydrogen, nitrogen and oxygen atoms are $8.16\times 10^{-5}mol$, $2.04\times 10^{-4}mol$, $4.08\times 10^{-5}mol$ and $8.16\times 10^{-5}mol$ respectively.

• For c:

Mass of Treflan = 25 lbs = 11350 g   (Conversion factor: 1 lbs = 454 g)

Molar mass of Treflan = 283.28 g/mol

Putting values in equation 1, we get:

$\text{Moles of Treflan}=\frac{11350g}{283.28g/mol}=40mol$

In 1 mole of treflan, 13 moles of carbon atoms, 16 moles of hydrogen atoms, 2 mole of nitrogen atom, 4 moles of oxygen atoms and 1 mole of fluorine are present.

So, in 40.03 moles of treflan, $(13\times 40)=520mol$ of carbon atoms, $(16\times 40)=640mol$ of hydrogen atoms, $(2\times 40)=80mol$ of nitrogen atoms, $(4\times 40)=160mol$ of oxygen atoms and $(1\times 40)=40mol$ of fluorine atoms are present.

Thus, the number of moles of compound is 40 moles and number of moles of carbon, hydrogen, nitrogen, oxygen and fluorine atoms are 520 moles, 640 moles, 80 moles, 160 moles and 40 moles respectively.

• For d:

Mass of Paris green = 0.125 kg = 125 g    (Conversion factor: 1 kg = 1000 g)

Molar mass of Paris green = 618.11 g/mol

Putting values in equation 1, we get:

$\text{Moles of Paris green}=\frac{125g}{618.11g/mol}=0.202mol$

In 1 mole of Paris green, 4 moles of carbon atoms, 6 moles of hydrogen atoms, 4 moles of copper atom, 10 moles of oxygen atoms and 2 moles of arsenic are present.

So, in 0.202 moles of Paris green, $(4\times 0.202)=0.808mol$ of carbon atoms, $(6\times 0.202)=1.212mol$ of hydrogen atoms, $(4\times 0.202)=0.808mol$ of copper atoms, $(10\times 0.202)=2.02mol$ of oxygen atoms and $(2\times 0.202)=0.404mol$ of arsenic atoms are present.

Thus, the number of moles of compound is 0.202 moles and number of moles of carbon, hydrogen, copper, oxygen and arsenic atoms are 0.808 moles, 1.212 moles, 0.808 moles, 2.02 moles and 0.404 moles respectively.

• For e:

Mass of Aspirin = 325 mg = 0.325 g    (Conversion factor: 1 g = 1000 mg)

Molar mass of aspirin = 180.16 g/mol

Putting values in equation 1, we get:

$\text{Moles of aspirin}=\frac{0.325g}{180.16g/mol}=0.0018mol$

In 1 mole of aspirin, 9 moles of carbon atoms, 8 moles of hydrogen atoms and 4 moles of oxygen atoms are present.

So, in 0.0018 moles of aspirin, $(9\times 0.0018)=0.0162mol$ of carbon atoms, $(8\times 0.0018)=0.0144mol$ of hydrogen atoms and $(4\times 0.0018)=0.0072mol$ of oxygen atoms are present.

Thus, the number of moles of compound is 0.0018 moles and number of moles of carbon, hydrogen and oxygen are 0.0162 moles, 0.0144 moles and 0.0072 moles respectively.