Question

A group 2 metal carbonate has a mass of 84 g/mol. Identify the group 2 metal X using its chemical formula.

Please show your working out. number of moles in 0.3g of calcium carbonate.

Answer 1

Answer:

Magnesium

0.003mole

Explanation:

The problem here entails we find the metal in the carbonate.

 For group 2 member, let the metal  = X;

 The carbonate is XCO₃;

 If we sum the atomic mass of the elements in the metal carbonate, we should arrive at 84g/mol

 Atomic mass of C = 12g/mol

                            O  = 16g/mol

 Atomic mass of X + 12 + 3(16)  = 84

  Atomic mass of X  = 84 - 60  = 24g/mol

The element with atomic mass of 24g is Magnesium

B.

Number of moles in 0.3g of CaCO₃:

     Molar mass of CaCO₃   = 40 + 12 + 3(16)  = 100g/mol

 Number of moles = $\frac{mass}{molar mass}$  

 Number of moles  = $\frac{0.3}{100}$   = 0.003mole