Moles, Formulae and Reacting Quantities

The mole counts entities: one mole contains the Avogadro constant of those specified entities. Use $n=m/M$ for mass and molar mass, and $n=cV$ for solutions with volume in dm³ when concentration is mol dm⁻³. The balanced equation then connects amounts, not masses directly. Divide each available amount by its coefficient to identify the limiting reactant. Use that reactant to predict the maximum product; excess reagent does not increase the theoretical yield.

In $pV=nRT$, pressure must be in Pa, volume in m³ and temperature in kelvin when R is 8.31 J mol⁻¹ K⁻¹. Do not insert a room-temperature molar gas volume unless its conditions apply. For an empirical formula, divide each mass or percentage by its relative atomic mass, then divide by the smallest amount. Multiply all ratios if needed to reach whole numbers. The molecular formula is an integer multiple of the empirical formula, using the measured relative molecular mass.

Percentage yield compares actual and theoretical amounts of the same product. Atom economy compares the formula mass of the desired products with all products from the balanced equation, including coefficients. A process can have high yield and poor atom economy. A titration requires a measured aliquot, a suitable indicator and concordant titres. Calculate the mean from suitable concordant results, not the rough run. Burette uncertainty involves two readings; relative uncertainty becomes larger when the titre is small.

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