Question

calculate thr no. of moles in (a) 52 g of He (b) 12.044 x 10^23.

Answer 1

Calculate nº of moles in:

a) 52 g of He

Molar Mass of He = 4 g/mol, therefore:
4 g → 1 mol
52 g → y

Solving: Rule of three (directly proportional)
$\frac{4}{52} = \frac{1}{y}$
multiply cross
$4*y = 52*1$
$4y = 52$
$\boxed{\boxed{y = 13\:mols}}\end{array}}\qquad\quad\checkmark$


Calculate nº of moles in:

b) 12.044*10²³

If:
Constant of avogrado
1 mol → 6.02*10²³ molecules
Therefore:
y mol → 12.044*10²³ molecules

Solving: Rule of three (directly proportional)
$\frac{1}{y} = \frac{6.02*10^{23}}{12.044*10^{23}}$
multiply cross
$6.02*10^{23}y = 12.044*10^{23}$
$y = \frac{12.044*\diagup\!\!\!\!\!10^{23}}{6.02*\diagup\!\!\!\!\!10^{23}}$
$\boxed{\boxed{y \approx 2.00\:mols}}\end{array}}\qquad\quad\checkmark$