Question

5. Find the percent composition (by mass) of nickel (II) hydroxide. % Ni = %0= % H = a. Use your answer to #5 to the determine the mass of nickel in 45.0 g of nickel (II) hydroxide. b. Use your answer to #5 to determine the mass of nickel (II) hydroxide that contains 10.0 g of nickel.

Answer 1

Sol. 5 - We know that Molar mass of NI(OH)2 = 92.7 g/mol, which means that 1 momle of NI(OH)2 will have mass of 92.7 g, and this mass is composed of Ni, O, and H molar mass.

Thus, MOlar mass of Ni = 58.7 g/mol

MOlar mass of O = 16 g/mol

MOlar mass of H = 1 g/mol

Ni(OH)2 has -

One Ni = 58.7 g/mol

Two O = 2 * 16 = 32 g/mol

Two H = 2 * 1 = 2 g/mol

Hence, for one mole of NI(OH)2 , % mass of each will be given as -

% mass of Ni = (molar mass of Ni / Molar mass Of NI(OH)2 ) * 100

% Mass of Ni = (58.7 / 92.7 ) * 100 = 63.32 %

% Mass of O = (32 / 92.7 ) * 100 = 34.52 %

% Mass of H = (2 / 92.7 ) * 100 = 2.157 %

a -

Given that mass of Ni(OH)2 = 45 g

No of moles = mass / molar mass

no of moles = 45 / 92.7 = 0.4854 mols

One mole of NI(OH)2 has mass of Ni = 58.7 g

Thus, 0.4854 mole will have Ni mass = 58.7 * 0.4854 = 28.4929 g

B-

Given mass of Ni = 10 g

58.7 g Ni makes Ni(OH)2 = 92.7 g

1 g -------------------- = 92.7/58.7 =1.579 g

Thus 10 g of Ni makes Ni(OH)2 = 1.579 * 10 = 15.79 g of Ni(OH)2