Calculate the molarity of each of the following solutions:
(a) 293 gram hcl in 666 ml of solution, a concentrated hcl solution
(b)2.026 g in 0.1250 ml of a solution used as an unknown in general chemistry laboratory
(c) 0.001 mg cd2+ in 0.100 l the maximum permissible concentration of cadmium in drinking water
(d) 0.0079 g c7h5sno3 in one ounce(29.6ml), concentration of saccharin in a diet soft drink

Explanation:

Molarity  is the number of moles or grammes of a substance present in one dm³ of a solution. Molarity is often expressed in the unit of moldm⁻³.

Molarity  =

Molarity =

(a) 293 gram HCL in 666 ml of solution, a concentrated HCL solution

We are given:

Mass of HCl = 293g

Volume of solution = 666ml

Unknown:

Molarity of HCl

Let us convert the volume into dm³:

             1000mL = 1dm³

               666mL = dm³ , 0.666dm³

Now, we solve for molarity:

Molarity =

The number of moles is unknown and can be derieved from the equation below:

Number of moles of HCl =

Molar mass of HCl = 1 + 35.5 = 36.5gmol⁻¹

Number of moles of HCl =   = 8.03mole

Now we proceed to find molarity:

Molarity = = 12.06moldm⁻³

(b)2.026 g in 0.1250 ml of a solution used as an unknown in general Chemistry laboratory:

Given parameters:

Mass of solute = 2.062g

Volume of solution = 0.1250mL

Unkown:

Molarity of the solution

Since molarity simply expresses the amount of solute in a substance, we can also use the express below:

Molarity = = = 16.496g/mL

(c) 0.001 mg Cd2+ in 0.100 L the maximum permissible concentration of cadmium in drinking water

Given parameters:

mass of cadmium ions = 0.001mg

Volume of solution = 0.1L

Unknown:

Molarity of the solution =?

Molarity = =   = 0.01mg/L

(d) 0.0079 g C7H5SNO3 in one ounce(29.6mL), concentration of saccharin in a diet soft drink:

Given parameters:

Mass of saccharin, C₇H₅SNO₃  = 0.0079g

Volume of solution = 29.6mL

Unknown:

Molarity = ?

Molarity = = = 0.00027g/mL