Reacting Masses Gases And Yields
A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Its relative molecular mass is 180.0. What is its molecular formula?
Calculate the mass of carbon dioxide released when 12.5 g of calcium carbonate decomposes completely: CaCO₃(s) → CaO(s) + CO₂(g). [Mr(CaCO₃) = 100.1, Mr(CO₂) = 44.0]
A student is determining the molar volume of hydrogen by reacting magnesium with excess HCl, collecting H₂ over water. Which error would cause the calculated molar volume to be lower than the true value of 24.0 dm³ mol⁻¹?
A volatile liquid of mass 0.342 g vaporises to occupy 120 cm³ at 87 °C and 101 kPa. What is its relative molecular mass? (R = 8.31 J K⁻¹ mol⁻¹)
Hydrated copper(II) sulfate, CuSO₄·xH₂O, has a mass of 2.50 g. After heating to constant mass, 1.60 g of anhydrous CuSO₄ remains. What is the value of x? [Mr(CuSO₄) = 159.6, Mr(H₂O) = 18.0]
In the reaction 2H₂(g) + O₂(g) → 2H₂O(l), what is the percentage atom economy for water as the desired product?
Which statement correctly distinguishes percentage yield from percentage atom economy?
0.0972 g of magnesium reacts completely with excess dilute HCl. What volume of hydrogen, measured at RTP, is produced? [Ar(Mg) = 24.3, molar volume = 24.0 dm³ mol⁻¹]
Which ionic equation, with correct state symbols, represents the reaction between aqueous lead(II) nitrate and aqueous potassium iodide?
When chlorine water is added to colourless aqueous potassium bromide, the solution turns orange. Which ionic equation correctly describes this observation?
A student claims that boosting percentage yield from 70% to 95% in an industrial reaction will always make the process “greener”. Which statement best evaluates this claim?
A scuba diver is preparing a gas mixture at 250 kPa and 25 °C. They need to know the number of moles of oxygen in a 12.0 dm³ cylinder. Which calculation gives the correct value? (R = 8.31 J K⁻¹ mol⁻¹)
4.60 g of ethanol (C₂H₅OH) is oxidised to produce 3.80 g of ethanoic acid (CH₃COOH). What is the percentage yield? [Mr(C₂H₅OH) = 46.0, Mr(CH₃COOH) = 60.0]
Why does one mole of any gas occupy the same volume at room temperature and pressure, regardless of the identity of the gas?
In Core Practical 1, which variable is best classified as a control variable rather than independent or dependent?
When dilute sulfuric acid is added to solid copper(II) carbonate, effervescence is observed and the solid dissolves to form a blue solution. Which ionic equation best represents this reaction?