14.8 g of a salt (z)dissolved in 250 cm³ of distilled water gives a concentration of 0.80 mol dm^-3. Calculate the molar mass of the salt (z).

Faramaye

1 year ago

convert the volume from cm3 to dm3
250cm=250/1000=0.25dm3
moles=concentration x volume
=0.80mol/dm3 x 0.5dm3
=0.2 mol
molar mass =mass/moles
=14.8/0.2=74g/mol

innogson

1 year ago

What are we given?
Mass of salt (z) = 14.8 g

Volume of solution = 250 cm³ = 0.250 dm³

Concentration = 0.80 mol/dm³

Required: Molar mass (M) of the salt (z)

Step 1: Use the formula for concentration
Concentration
=
Number of moles
Volume in dm
3
Concentration=
Volume in dm
3

Number of moles
​

Rearranging:

Number of moles
=
Concentration
×
Volume
Number of moles=Concentration×Volume
Number of moles
=
0.80
×
0.250
=
0.20
mol
Number of moles=0.80×0.250=0.20 mol
Step 2: Use the formula for molar mass
Molar Mass (M)
=
Mass
Number of moles
=
14.8
0.20
=
74.0
g/mol
Molar Mass (M)=
Number of moles
Mass
​
=
0.20
14.8
​
=74.0 g/mol
Final Answer:
D. 74.0 g mol⁻¹