Question

Having done the experiment, explain briefly how the mass of zinc not equal the mass of lead gained (hint: the periodic table)

Answer 1

Answer:

Due to the difference in the relative atomic masses and therefore, the molecular masses of Zn and Pb, one mole of Zn is about 3.2 times lighter than one mole of Pb

Explanation:

From the periodic table, we have;

The atomic number of zinc, Zn = 30

The atomic mass of zinc, Zn = 65.38 amu

The molar mass of zinc, Zn = 65.38 g/mol

The atomic number of lead, Pb = 82

The atomic mass of lead, Pb = 207.2 amu

The molar mass of lead, Pb = 207.2 g/mol

Therefore, whereby equal number of moles of Zn is lost and Pb is gained, we have;

Mass of 1 mole of Zn = 65.38 grams

Therefore, 1 gram of Zn = 1/65.38 moles = 0.0153 moles

0.12 grams of Zn = 0.12×0.0153 = 0.00184 moles of Zn

Given that equal number of moles of Zn and Pb are involved in the reaction, the number of moles of Pb gained = 0.00184 moles

The mass of Pb gained = Number of moles of Pb gained × Molar mass of Pb

The mass of Pb gained = 0.00184 × 207.2 = 0.38 g ≈ 0.4 g.

Amount of Pb gained = 0.43 g ≈ 0.4 g