The ratio of mass of 'x' atoms of an element to mass of carbon atoms is 9:1. Find the mass of 1 mol of x if molar mass of carbon is 12 g/mol.

Let the mass of one atom of element 'x' be $m_x$ and the mass of one carbon atom be $m_C$.

Given that the ratio of the mass of an atom of element 'x' to the mass of a carbon atom is $9:1$, we have:

$\dfrac{m_x}{m_C} = \dfrac{9}{1}$

The ratio of their molar masses is equal to the ratio of their atomic masses:

$\dfrac{M_x}{M_C} = 9$

Given the molar mass of carbon, $M_C = 12\ \text{g/mol}$, the molar mass of element 'x' is:

$M_x = 9 \times 12 = 108\ \text{g/mol}$

Therefore, the mass of $1\ \text{mol}$ of element 'x' is $108\ \text{g}$.