Question

The mass of $CaC{O_3}$ required to react completely with 50ml of 0.5 M HCl is:
(a) 10 g
(b) 1.25 g
(c) 5 g
(d) 2.5 g

Answer 1

Molarity can be used to find out the mass as it indicates the number of moles of solute per litre of solution (moles/Litre) and is one of the most common units used to measure the concentration of a solution.

Complete step by step answer:
We have been provided with:
Volume of HCl: V= 50ml = 0.05L
Molarity of HCl: M= 0.5M
Use the molecular formula to find the molar mass; to obtain the number of moles, divide the mass of compound by the molar mass of the compound expressed in grams
So, we can find the number of moles using the formula: molarity × volume= 0.5×0.005
So, the number of moles comes out to be: 0.025mol
Now, $CaC{O_3} + 2HCl \to CaC{l_2} + C{O_2} + {H_2} O$
Therefore, the moles of $CaC{O_3}$ required: $n = \dfrac{{{n_{HCl}}}}{2}$=$\dfrac {{0.025}}{2}$,
Therefore, mass of $CaC{O_3}$ required: ${W_1} = {n_1} \times {M_{CaC{O_3}}}$
So, it comes out to be: $\dfrac {{0.025}}{2} \times 100 = 1.25g$
So, we can say that the mass of $CaC{O_3}$ required to react completely with 50ml of 0.5 M HCl is 1.25g.
So, the correct answer is “Option B”.

Note: A mole is the mass of a substance which consists of the equal quantity of basic units. Example atoms in 12 grams are the same as 12C. The basic units can be molecules, atoms or formula units based on the substance.