Question

Question #08917

Answer 1

1
`0.3 * 1.204 * 10^24 = 3.612 * 10^23` H atoms
`0.7 * 1.204 * 10^24 = 8.428 * 10^23` atoms of unknown element

2
`3.612 * 10^23` H atoms `* 1/(6.022 * 10^23)` mol/atoms `* 1.01/1` g/mol = 0.606g

So, `57.14 - 0.606` = 56.53g

3
`8.428 * 10^23 * 1/(6.022 * 10^23) = 1.3995` mol of unknown element

Molar mass = `56.53/1.3995 = 40.3` gmol

With slight error, this is the molar mass of argon on the periodic table (i.e 39.95 g/mol).