Questions: How many moles of Cr2(CO3)3 are in 100.0 g ?

Solution Steps

To find the molar mass of \(\mathrm{Cr}_{2}\left(\mathrm{CO}_{3}\right)_{3}\), we need to sum the atomic masses of all the atoms in the formula:

• Chromium (Cr): The atomic mass is approximately 51.9961 g/mol. There are 2 Cr atoms, so the total mass is \(2 \times 51.9961 = 103.9922\) g/mol.
• Carbon (C): The atomic mass is approximately 12.011 g/mol. There are 3 carbonate ions, each containing 1 carbon atom, so the total mass is \(3 \times 12.011 = 36.033\) g/mol.
• Oxygen (O): The atomic mass is approximately 15.999 g/mol. Each carbonate ion contains 3 oxygen atoms, so there are \(3 \times 3 = 9\) oxygen atoms in total, giving a total mass of \(9 \times 15.999 = 143.991\) g/mol.

Adding these together gives the molar mass of \(\mathrm{Cr}_{2}\left(\mathrm{CO}_{3}\right)_{3}\):

\[ 103.9922 + 36.033 + 143.991 = 283.0162 \, \text{g/mol} \]

To find the number of moles of \(\mathrm{Cr}_{2}\left(\mathrm{CO}_{3}\right)_{3}\) in 100.0 g, use the formula:

\[ \text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \]

Substituting the given values:

\[ \text{moles} = \frac{100.0 \, \text{g}}{283.0162 \, \text{g/mol}} = 0.3533 \, \text{mol} \]

Final Answer