Question

4.6 x 10²² molecules of a compound weigh 13.8g. If N_A = 6 x 10²³ calculate the molecular weight of this compound

Based on the molecular weight calculated for the question, give a probable chemical name of the compound and writes its molecular formula

Answer 1

The molecular weight of the compound can be calculated as.

• 1 mole contains an Avogadro number of molecules.N_A = 6 x 10²³ and it contains the molecular weight of the substance.

$No.ofmoles=\frac{givenmass}{grammolecularmass}$

• The unknown number of moles in 4.6 x 10²² is

$$\begin{gathered} No.ofmoles=\frac{no.ofmolecules}{avagadronumber} \\ =\frac{4.6x{10}^{22}}{6x{10}^{23}} \\ =0.076moles \end{gathered}$$

• The molecular weight of this compound

$$\begin{gathered} Grammolecularmass=\frac{givenmass}{no.ofmoles} \\ =\frac{13.8}{0.076} \\ =181.57g \end{gathered}$$

Based on the molecular weight calculated, a probable chemical name of the compound is dichlorine heptoxide. and its molecular formula ${\mathrm{Cl}}_2{\mathrm{O}}_7$.