Question

Calculate the Molar Mass Please select either A,B,C, or D at the end.

Answer 1

To calculate the molar mass of a compound, we first need to get the molar masses of the elements on the compond.

We can check thouse on a periodic table. In this case, we have the atoms Ca, N and O, so:

`\begin{gathered} M_(Ca)=40.08g\/mol \\ M_N=14.01g\/mol \\ M_O=16.00g\/mol \end{gathered}`

The molar mass of the compound will be the sum of the molar mass of the elements multiplied by the amount of thouse elements are in the compound.

The parenthesis in the formula of Ca(NO₃)₂ means that there are two groups of NO₃, so there are 1 atom of Ca, 2 atoms of N and 6 atoms of O, thus, the molar mass is:

`\begin{gathered} M_(Ca\mleft(NO_3\mright)_2)=1\cdot M_(Ca)+2\cdot M_N+6\cdot M_O \\ M_(Ca(NO_3)_2)=(1\cdot40.08+2\cdot14.01+6\cdot16.00)g\/mol \\ M_(Ca(NO_3)_2)=(40.08+28.02+96.00)g\/mol \\ M_(Ca(NO_3)_2)=164.10g\/mol\approx164.1g\/mol \end{gathered}`

As we can see, this corresponds to alternative C.