Question

What is the mass of $ 1.2 \times {10^{18}} $ formula units of calcium chloride?

Answer 1

Hint: Calcium chloride is an inorganic salt with the molecular formula of $ CaC{l_2} $ . The molar mass of calcium chloride is $ 110.98gmo{l^{ - 1}} $ . The amount of substance can be expressed in different units like moles and grams, where one mole is equal to $ 6.023 \times {10^{23}}units $ . The formula units can be converted into grams by multiplying the molar mass and dividing with Avogadro’s number.

Complete Step By Step Answer:
The amount of chemical compounds can be expressed in different units like grams and moles. Where one mole is equal to $ 6.023 \times {10^{23}}units $ the units may be molecules, ions or atoms. Calcium chloride is an inorganic salt formed by the combination of calcium and two chlorine atoms. The chemical formula of calcium chloride is $ CaC{l_2} $ . The molar mass of calcium chloride is $ 110.98gmo{l^{ - 1}} $ .
Given that the formula units of calcium chloride are $ 1.2 \times {10^{18}} $
To know the mass of these $ 1.2 \times {10^{18}} $ formula units of calcium chloride the ratio of molar mass of calcium chloride and value of one mole should be taken, as one mole of calcium chloride has $ 6.023 \times {10^{23}}units $ and has the mass of $ 110.98g $
The mass of a given sample will be
 $ 1.2 \times {10^{18}}f.units \times \dfrac{{110.98g}}{{6.023 \times {{10}^{23}}f.units}} = 2.2 \times {10^{ - 4}}g $
Thus, the mass of $ 1.2 \times {10^{18}} $ formula units of calcium chloride is $ 2.2 \times {10^{ - 4}}gm $ .

Note:
While calculating the mass from formula units, the Avogadro’s number and the molar mass has to be taken, as Avogadro’s number is the number of molecules or ions in one mole. The molar mass taken should be in grams but not in $ gmo{l^{ - 1}} $ as we are taking the molar mass of one mole.