When 5.91 g of bivalent metal carbonate interacted with an excess of hydrochloric acid, 672 ml of gas were released.

1. Let’s write the equation schematically:
MeCO3 + 2HCl = MeCl2 + H2O + CO2 – ion exchange reaction, carbon monoxide is released (4);
2. Let’s translate the units of volume:
V (CO2) = 672 ml. = 0.672 l.
3. Let’s make the proportion:
1 mole of gas at normal level – 22.4 liters;
X mol (CO2) – 0.672 L. hence, X mol (CO2) = 1 * 0.672 / 22.4 = 0.03 mol;
Y (MeCl2) = 0.03 mol since the amount of these substances according to the equation is equal to 1 mol.
4. Find the molar mass of salt:
M (MeCO3) = m / Y = 5.91 / 0.03 = 197 g / mol;
M (Me) = 197 – 60 = 137 g / mol.
5. Ba – bivalent metal;
Ar (Ba) = 137.3 (according to the table of the Periodic Table of D.I.Mendeleev)
Answer: the metal is barium.