Question

how many litres of 0.500M HCL(aq) are needed to react completely with 0.100 mol of Pb(NO3)2, forming a precipitate of PbCl2(s)...please explain

Answer 1

The volume that is needed to react completely with 0.100 mol of lead nitrate is 0.400 L. It is because 2 moles of HCl are required for every mole of lead nitrate.
2 x 0.100 mole Pb(NO₃) = 0.200 mole HCl 
0.200 mol HCl = L x 0.500 M 

Answer 2

Explanation:

Molarity is defined as the number of moles present in a liter of volume.

Mathematically,      Molarity = $\frac{\text{no. of moles}}{Volume}$

As it is given that molarity is 0.50 M and no. of moles is 0.1 mol. Hence, we will calculate the volume of given solution as follows.

                 Molarity = $\frac{\text{no. of moles}}{Volume}$

                     0.5 M = $\frac{0.1 mol}{Volume}$

                   Volume = $\frac{0.5 M}{0.1 mol}$

                                 = 5 liter

Thus, we can conclude that 5 liters of 0.500M HCl (aq) are needed to react completely with 0.100 mol of $Pb(NO_{3})_{2}$, forming a precipitate of $PbCl_{2}(s)$.