Question

4.) A In an experiment, 1.056 g of a metal carbonate,

containing an unknown metal M, is heated to give the
metal oxide and 0.376 g CO2.
MCO3(s) + heat → MO(s) + CO2(g)
What is the identity of the metal M?
(a) M = Ni
(c) M = Zn
(b) M = Cu
(d) M = Ba
1​

Answer 1

M= Cu

Step-by-step explanation:

From the question;

Mass of metal carbonate = 1.056 g

Mass of CO₂ = 0.376 g

We are required to identify the metal M in the carbonate

The equation for the combustion of the carbonate;

MCO₃(s) + heat → MO(s) + CO₂(g)

Step 1: Calculating the number of moles of CO₂

Moles = Mass ÷ molar mass

Molar mass CO₂ = 44.01 g/mol

Moles = 0.376 g ÷ 44.01 g/mol

= 0.00854 Moles

Step 2: Determining the moles of MCO₃

From the equation;

1 mole of the metal carbonate decomposes to yield 1 mole CO₂

Therefore; Mole ratio of MCO₃ : CO₂ = 1 : 1

Hence; Moles of MCO₃ = 0.00854 moles

Step 3: Determining the molar mass of MCO₃

Moles of MCO₃ = 0.00854 moles

Mass of the carbonate = 1.056 g

But;

Molar mass = Mass ÷ moles

= 1.056 g ÷ 0.00854 moles

= 123.65 g/mol

Step 4: Atomic mass of the metal

The molar mass of metal carbonate = 123.65 g/mol

Atomic mass of carbon = 16

Atomic mass of oxygen = 12.01

Therefore;

123.65 g = M + 12.01 + (16 ×3)

M = 63.64 g

The atomic mass of M is 63.64 approximately the same as that of copper.

Atomic mass of Cu is 63.546

Therefore, identity of M is Cu