A student makes barium sulfate, an insoluble salt.
The student mixes barium chloride solution with sodium sulfate solution. A white precipitate of barium sulfate forms.
BaCl2+Na2SO4→BaSO4+2NaCl \mathrm{BaCl_{2}} + \mathrm{Na_{2}SO_{4}} \rightarrow \mathrm{BaSO_{4}} + 2\mathrm{NaCl} BaCl2+Na2SO4→BaSO4+2NaClThe student filters off the precipitate, washes it with distilled water and dries it.
The student uses 5.00 g of barium chloride.
Calculate the maximum mass of barium sulfate that could be made.
Give your answer to 3 significant figures.
Relative atomic mass (Ar): Ba = 137.3 Cl = 35.5 O = 16.0 S = 32.1
Maximum mass = ...... g
The student makes 4.90 g of dry barium sulfate.
Calculate the percentage yield.
Percentage yield = ...... %
Suggest one reason why the percentage yield is less than 100%.
Calculate the atom economy for making barium sulfate in this reaction.
Use the equation: atom economy = (Mr of desired product ÷ total Mr of all products) × 100
Relative atomic mass (Ar): Na = 23.0
Atom economy = ...... %
The student says:
"The percentage yield is 87.5%, so 12.5% of the atoms in the reactants end up in waste products. The atom economy will be 87.5% too."
Evaluate the student's statement.
57 exam-style questions on OCR GCSE Chemistry 5.1 Monitoring chemical reactions, covering 5.1.1 The technique of titration, 5.1.2 Theoretical mass, percentage yield and atom economy, 5.1.3 Concentration of a solution in mol/dm3, 5.1.4 Concentration calculations and titration results, 5.1.5 Molar gas volume and volumes of gases in reactions, and 5.1.6 Choosing a reaction pathway. Each one has a worked solution and a mark scheme showing where the marks go.