Question

What is the mass of 1.56 x 1023 atoms of aluminum?

Answer 1

The molecular weight of Aluminum $=26.98g/mol$

The mass of Aluminum is unknown hence $(x)$

Atoms of Aluminum$=1.56\times 10^{23}$

In determination of the unknown value, we convert from Atoms$\to$ Moles$\to$ Mass

Atoms$\to$ Moles

Moles of Aluminum( using Avogadros constant) is also unknown$(y)$

$6.022\times10^{23}Al\over1molAl$ $\times ymol Al=1.56\times10^{23}AtomsAl$

$y mol Al=$$1.56\times 10^{23} \over 6.022\times 10^{23}$ $=0.259mol Al$

Moles$\to$ Mass

$xgAl\times$ $1molAl\over 26.98gAl$ $=0.259 mol Al$ .

$xgAl=(0.259 mol Al\times 26.98g/mol) =6.98g Al$

The Mass is thus $6.98g$