Answer:
1.89g of HNO3
Explanation:
Data obtained from the question include:
Mass of water = 31.5 g
Molality of HNO3 = 0.950 m
Mass of HNO3 =.?
Next, we shall determine the number of mole of HNO3 in the solution.
Mass of water = 31.5 g = 31.5/1000 = 0.0315 Kg
Molality of HNO3 = 0.950 m
Number of mole of HNO3 =..?
Molality is simply defined as the mole of solute per unit kilogram of solvent (water) i.e
Molality = mole /kg of water
With the above formula, the mole of HNO3 can be obtained as follow:
Molality = mole /kg of water
0.950 = mole of HNO3 /0.0315
Cross multiply
Mole of HNO3 = 0.950 x 0.0315
Mole of HNO3 = 0.03 mole
Finally, we shall convert 0.03 mole of HNO3 to grams. This is illustrated below:
Molar mass of HNO3 = 1 + 14 + (16x3) = 63g/mol
Mole of HNO3 = 0.03 mole
Mass of HNO3 =..?
Mole = mass /molar mass
0.03 = mass of HNO3 /63
Cross multiply
Mass of HNO3 = 0.03 x 63
Mass of HNO3 = 1.89g
Therefore, 1.89g of HNO3 is needed to prepare the solution.
