Question

Write the names of the following compounds and deduce their molecular masses.
(A)$N{a_2}S{O_4}$
(B)${K_2}C{O_3}$
(C)$C{O_2}$
(D)$MgC{l_2}$
(E)$NaOH$
(F)$AlP{O_4}$
(G)$NaHC{O_3}$

Answer 1

As we know that the elements have a particular name and the compounds possess a specific name according to the number of atoms and the elements present in the whole compound. We also know that the molecular mass of any compound can be calculated by simply adding the masses of the individual element or atoms.

Complete answer:
We are very well aware of the naming system of the compounds which are formed by the mixing or combination of two different atoms or molecules. We also know that molecular mass is basically the sum of atomic weight of the number of atoms of all the elements present in a compound.
In the above options we can see that two or more than two elements are combining to form a compound, so let us name these compounds one by one and identify their molecular masses.
(A) $N{a_2}S{O_4}$: As we can see that sodium and sulphate are combining to form the sodium sulphate and we know that the atomic mass of sodium is $23g$, the atomic mass of sulphur is $32g$ and oxygen has an atomic mass as $16g$. So, this compound will have a molecular weight as calculated below:
$molecular\;weight = 23 \times 2 + 32 + 16 \times 4 \\\ \Rightarrow 46 + 32 + 64 \\\ \Rightarrow 142g \\\$
Similarly, we can calculate and name the other compounds.
(B) ${K_2}C{O_3}$: The name of this compound is potassium carbonate and the molecular mass of potassium carbonate is as calculated below:
$molecular\;weight = 39 \times 2 + 12 + 16 \times 3 \\\ \Rightarrow 78 + 12 + 48 \\\ \Rightarrow 138g \\\$
(C) $C{O_2}$: this compound is carbon dioxide which possess a molecular mass as calculated below:
$molecular\;weight = 12 + 16 \times 2 \\\ \Rightarrow 12 + 32 \\\ \Rightarrow 44g \\\$
(D) $MgC{l_2}$: The name of this compound is magnesium chloride which possess a molecular mass as: $molecular\;weight = 24 + 35.5 \times 2 = 95g$
(E) $NaOH$: This is sodium hydroxide and the molecular mass of this compound is as calculated below:
$molecular\;weight = 23 + 16 + 1 = 40g$
(F) $AlP{O_4}$: This compound contains an aluminium and phosphate group thereby giving it a name aluminium phosphate and the molecular mass or molecular weight of the compound is as calculated below:
$molecular\;weight = 27 + 31 + 16 \times 4 \\\ \Rightarrow 27 + 31 + 64 \\\ \Rightarrow 122g \\\$
(G) $NaHC{O_3}$: This compound is sodium bicarbonate or simply sodium hydrogen carbonate and the molecular mass of this compound is:
$molecular\;weight = 23 + 1 + 12 + 16 \times 3 \\\ \Rightarrow 23 + 1 + 12 + 48 \\\ \Rightarrow 84g \\\$

Note: Always remember that the molecular weight of any compound is always calculated by the addition of the atomic weights of each individual element multiplied by the number of atoms present in that compound.