Question

5. A sample of sodium has a mass of 46 g. What is the mass of the same number of calcium atoms
as sodium atoms present in given sample ?
​

Answer 1

Answer: 80 g.

Explanation: Given ,

Weight of sodium = 46 g.

Molar mass of sodium = 23 g.

Molar mass of Ca = 40 g.

Moles of Na = weight ÷ Molar mass

= 46 ÷ 23

= 2 moles.

Moles of Na = Moles of Ca .... ( As per the question says..)

Moles of Ca = weight ÷ Molar mass

2 = weight ÷ 40

2 × 40 = weight.

80 g = weight of Ca

Answer 2

Answer:

Explanation: Correct option is

D

80g

= atomic mass of sodium= 23 g/mol

moles of sodium atoms in 46 gm= 46/23 = 2 moles

as mentioned in question, no of Na atoms = no of atoms of Ca atoms.

therefore no of atoms of ca atoms= 2 moles

therefore mass of 2 moles of Ca atoms = 2 x atomic wt of Ca = 2 mol x 40 g/mol = 80 g

Therefore answer is 80g.