Question

Calculate the no. of atoms of oxygen present in 88g of $\text{C}{{\text{O}}_{2}}$. What would be the weight of $\text{CO}$having the same number of oxygen atoms?
A. $\text{24}\text{.09 }\times \text{ 1}{{\text{0}}^{23}}\text{, 114g}$
B. $\text{24}\text{.08 }\times \text{ 1}{{\text{0}}^{25}}\text{, 112g}$
C. $\text{25}\text{.09 }\times \text{ 1}{{\text{0}}^{25}}\text{, 116g}$
D. $\text{24}\text{.09 }\times \text{ 1}{{\text{0}}^{23}}\text{, 112g}$

Answer 1

To solve the questions related to the mole concept one should know the atomic mass of each element like the atomic of carbon is 12 a.m.u and of oxygen 16 a.m.u. A number of moles is the ratio of the no. of atoms to the Avogadro's number.

Complete answer:
-It is given that the mass of carbon dioxide is 88h but we know that one of carbon dioxide has a mas of 44g i.e $\text{12 }\times \text{ (16 }\times \text{ 2) = 44g}$.
-So, it means that there are a total of two moles of carbon dioxide.
-Now, if one mole $\text{C}{{\text{O}}_{2}}$ has 2 oxygen atoms so the number of oxygen atoms in the 2 moles of $\text{C}{{\text{O}}_{2}}$will be: $2\text{ }\times \text{ 2 }\times \text{ 6}\text{.022 }\times \text{ 1}{{\text{0}}^{23}}\text{ = 24}\text{.09 }\times \text{ 1}{{\text{0}}^{23}}$.
-Now, we have to calculate the number of oxygen atoms in CO, as we know that there is 1 oxygen atom in CO.
-So, the mass of CO containing $\text{24}\text{.09 }\times \text{ 1}{{\text{0}}^{23}}$ oxygen atoms will be:
$\text{Mass = }\dfrac{\text{Molar mass }\times \text{ No}\text{. of atoms}}{\text{6}\text{.022 }\times \text{ 1}{{\text{0}}^{23}}}$
Here, mass is to be calculated and no. of atoms had calculated above i.e. $\text{24}\text{.09 }\times \text{ 1}{{\text{0}}^{23}}$.
-So, the mass will be: $\text{Mass = }\dfrac{28\text{ }\times \text{ 24}\text{.09 }\times \text{ 1}{{\text{0}}^{23}}}{6.022\text{ }\times \text{ 1}{{\text{0}}^{23}}}\text{ = 112g}$.
-Hence, 112g of carbon monoxide will have the same number of oxygen atoms as that in carbon dioxide.
So, the correct answer is “Option D”.

Note: The Law of multiple proportions states that when two elements together combine and forms more than one compound the mass of one element which combines with a fixed of the other element, will always give the whole number ratio. That's why we can say that the mass carbon in CO and $\text{C}{{\text{O}}_{2}}$ is the same i.e. 12g.