Answer:
6
Explanation:
The percent mass is equal to the ratio between the mass of the component of interest and the total mass of the compound, multiplied by 100 % in case we need to express it as a percentage.
We may apply this knowledge to write the formula for copper(II) nitrate x-hydrate. Let's assume that we take 1 mole of the compound. Then we will divide x molar masses of water by the molar mass of the overall compound and multiply by 100 % to get the mass percent of water:
[tex]\omega = \frac{xM_{H_2O}}{M_{total}}\cdot 100\%[/tex]
Here:
[tex]M_{H_2O} = 18.016 g/mol[/tex]
[tex]M_{total} = M_{Cu(NO_3)_2} + xM_{H_2O} = (187.56 + 18.016x) g/mol[/tex]
Substitute into the formula:
[tex]\frac{18.016x}{187.56 + 18.016x} = 0.365[/tex]
Solve for x:
[tex]18.016x = 0.365(187.56 + 18.016x)[/tex]
[tex]18.016x = 68.46 + 6.58x[/tex]
[tex]11.44x = 68.46\therefore x = 6[/tex]
