Equations, Moles and Chemical Calculations

A balanced chemical equation has the same number of each kind of atom on both sides. Change coefficients, not the subscripts inside correct formulae. Relative formula mass adds the relative atomic masses of all atoms in a formula unit. In a closed reaction system mass is conserved; an apparent mass change can occur if a gas enters or leaves an open container. The missing or gained gas is part of the mass balance.

One mole contains the Avogadro constant of the specified particles. Calculate amount with n = m/M, then apply the equation’s coefficient ratio before converting to the requested mass. When two reactants are supplied, compare their available amounts with the required ratio. The limiting reactant determines theoretical product. For solutions, concentration in g dm⁻³ equals mass divided by volume; molar concentration uses amount divided by volume. State which concentration unit is intended.

Percentage yield is actual product divided by theoretical product times 100. Atom economy measures the fraction of reactant atoms ending in the desired product, calculated from the balanced equation masses. Loss during transfer, incomplete reaction and competing reactions can lower yield. Wet or impure product can falsely increase measured yield. A gas-volume calculation needs the molar volume supplied for the stated conditions; do not assume a value applies at every temperature and pressure.

Attempt these problems on paper before opening the worked reasoning. Explain your steps as well as giving a final answer.