2HCl + Mg = MgCl2 + H2
Molar mass of Mg = 24 g/mol
24 g Mg = 1 mol Mg
4.8 g Mg = 0.2 mol Mg
According to the balanced equation, 1 mol of Mg produces 1 mol of H2
Therefore, 0.2 mol of Mg will produce 0.2 mol of H2
1 mol of any gas at STP occupies 22.4 L
Therefore, 0.2 mol of H2 will occupy 0.2 * 22.4 = 4.48 L of H2

Na2S + Pb$NO3$2 = PbS + 2NaNO3
Molar mass of Pb$NO3$2 = 331.2 g/mol
331.2 g Pb$NO3$2 = 1 mol Pb$NO3$2
132.4 g Pb$NO3$2 = 0.4 mol Pb$NO3$2
According to the balanced equation, 1 mol of Pb$NO3$2 produces 1 mol of PbS
Molar mass of PbS = 239.3 g/mol
Therefore, 0.4 mol of PbS will have a mass of 0.4 * 239.3 = 95.72 g

a) BaO + CO2 = BaCO3
Molecular equation: BaO + CO2 = BaCO3
Ionic equation: BaO + CO2 = Ba2+ + CO32-

b) BaO + H2SO4 = BaSO4 + H2O
Molecular equation: BaO + H2SO4 = BaSO4 + H2O
Ionic equation: BaO + 2H+ + SO42- = BaSO4 + H2O

c) BaO + 2NaOH = Ba$OH$2 + Na2O
Molecular equation: BaO + 2NaOH = Ba$OH$2 + Na2O
Ionic equation: BaO + 2Na+ + 2OH- = Ba2+ + 2OH- + 2Na+

d) BaO + H2O = Ba$OH$2
Molecular equation: BaO + H2O = Ba$OH$2
Ionic equation: BaO + 2H2O = Ba2+ + 2OH-

e) BaO + CuO = BaCuO2
Molecular equation: BaO + CuO = BaCuO2
Ionic equation: BaO + Cu2+ + O2- = Ba2+ + CuO2-

f) BaO + 2HBr = BaBr2 + H2O
Molecular equation: BaO + 2HBr = BaBr2 + H2O
Ionic equation: BaO + 2H+ + 2Br- = Ba2+ + 2Br- + H2O

4.
a) CO2 + ZnO = ZnCO3
Molecular equation: CO2 + ZnO = ZnCO3
Ionic equation: CO2 + Zn2+ + O2- = ZnCO3

b) CO2 + Ba$OH$2 = BaCO3 + H2O
Molecular equation: CO2 + Ba$OH$2 = BaCO3 + H2O
Ionic equation: CO2 + Ba2+ + 2OH- = BaCO3 + 2H2O

c) CO2 + 2HNO3 = H2CO3 + 2NO3-
Molecular equation: CO2 + 2HNO3 = H2CO3 + 2NO3-
Ionic equation: CO2 + 2H+ + 2NO3- = H2CO3 + 2NO3-

d) CO2 + H2O = H2CO3
Molecular equation: CO2 + H2O = H2CO3
Ionic equation: CO2 + H2O = H2CO3

e) CO2 + 2NaOH = Na2CO3 + H2O
Molecular equation: CO2 + 2NaOH = Na2CO3 + H2O
Ionic equation: CO2 + 2Na+ + 2OH- = 2Na+ + CO32- + H2O

f) CO2 + K2O = K2CO3
Molecular equation: CO2 + K2O = K2CO3
Ionic equation: CO2 + 2K+ + O2- = 2K+ + CO32-