Use a copy of the Periodic Table where you need one. One mole of any gas occupies 24 dm3 at room temperature and pressure.
Sodium hydrogencarbonate decomposes on heating. 2NaHCO3 → Na2CO3 + CO2 + H2O. In an experiment, 5.0 mol of sodium hydrogencarbonate was heated. What is the volume of carbon dioxide evolved, at room temperature and pressure?
Source: 2023 PLMGS Sec 3 End-of-Year P1 Q24
The atomic number of ruthenium is 44. One of the oxides of ruthenium is a black solid, X. 5.79 g of X contains 1.39 g of oxygen. What is the empirical formula of X?
Source: 2023 PLMGS Sec 3 End-of-Year P1 Q25
Which contains the greatest mass of solute?
Source: 2023 PLMGS Sec 3 End-of-Year P1 Q27
The forward reaction for the Haber process is N2(g) + 3H2(g) → 2NH3(g). 15 cm3 of nitrogen was added to 60 cm3 of hydrogen in a container. What is the total volume of gas remaining in the container after the reaction is complete?
Source: 2023 GESS Sec 3 End-of-Year P1 Q25
Carbon monoxide reacts with oxygen to form carbon dioxide: 2CO(g) + O2(g) → 2CO2(g). In this reaction, 3 moles of carbon monoxide and 2 moles of oxygen are mixed. When the reaction is complete, there will be
Source: SJI 2020 Year 3 End-of-Year P1 Q17
In a titration, 26.4 cm3 of 0.2 mol/dm3 aqueous calcium hydroxide was required to completely neutralise 19.0 cm3 of dilute hydrochloric acid. What is the concentration of the acid used?
Source: 2023 HYSS Sec 3 End-of-Year P1 Q18
20.0 cm3 of 0.100 mol/dm3 potassium hydroxide is completely reacted with 20.0 cm3 of sulfuric acid solution. What is the concentration of potassium ions in the resultant solution?
Source: SJI 2020 Year 3 End-of-Year P1 Q16
On adding 53 g of impure sodium carbonate, Na2CO3 (Mr = 106), to excess hydrochloric acid, 3.0 dm3 of CO2 was evolved at room temperature and pressure. What is the percentage purity of the sodium carbonate?
Source: 2023 GESS Sec 3 End-of-Year P1 Q28
Zinc blende is mainly zinc sulfide, ZnS. When it is burnt in air: 2ZnS(s) + 3O2(g) → 2ZnO(s) + 2SO2(g). 194 g of an impure zinc blende sample is burnt in excess oxygen to produce 43.2 dm3 of sulfur dioxide. What is the percentage purity of zinc sulfide in the sample?
Source: SJI 2020 Year 3 End-of-Year P1 Q18
Methane, CH4, is a commonly used gas for household cooking. 20 cm3 of methane and 60 cm3 of oxygen are reacted to form carbon dioxide and water as the only products.
Source: SJI 2020 Year 3 End-of-Year P2 A4
30.0 cm3 of 0.80 mol/dm3 nitric acid was reacted with 10 g of magnesium.
Source: 2023 GESS Sec 3 End-of-Year P2 B12(a)
Sodium hydride, NaH, is an ionic compound. In a reaction, 0.24 g of sodium hydride was reacted with 1.8 cm3 of water to form sodium hydroxide solution and hydrogen gas at r.t.p.
Source: 2024 SMSS Sec 3 End-of-Year P2 Q5(b)
A common antacid is magnesium hydroxide, Mg(OH)2, a base that is slightly soluble in water. 25.0 cm3 of a saturated solution of magnesium hydroxide required 27.60 cm3 of 0.220 mol/dm3 dilute hydrochloric acid for complete neutralisation.
Source: 2024 CHS Sec 3 End-of-Year Section B Q7
D60 dm3[1]
2 mol NaHCO3 give 1 mol CO2, so 5.0 mol give 2.5 mol. Volume = 2.5 × 24 = 60 dm3.
CRuO2[1]
Mass of Ru = 5.79 − 1.39 = 4.40 g. Moles: Ru = 4.40101 = 0.0436, O = 1.3916 = 0.0869. The ratio is 1 : 2.
C1.00 dm3 of 0.10 mol/dm3 potassium hydroxide, KOH[1]
A: 0.100 mol × 40 = 4.0 g. B: 0.025 mol × 98 = 2.45 g. C: 0.10 mol × 56 = 5.6 g. D: 0.02 mol × 36.5 = 0.73 g.
C45 cm3[1]
15 cm3 of N2 reacts with 45 cm3 of H2, so nitrogen is limiting and 15 cm3 of H2 is left. 30 cm3 of NH3 forms. Total = 15 + 30 = 45 cm3.
A0.5 mole of oxygen unreacted.[1]
3 mol of CO needs only 1.5 mol of O2, so 0.5 mol of O2 is left and 3 mol of CO2 forms.
C0.56 mol/dm3[1]
Ca(OH)2 + 2HCl → CaCl2 + 2H2O. Moles of Ca(OH)2 = 0.2 × 0.0264 = 0.00528 mol, so moles of HCl = 0.01056 mol. Concentration = 0.010560.0190 = 0.56 mol/dm3.
A0.050 mol/dm3[1]
Moles of K+ = 0.100 × 0.0200 = 0.00200 mol, now in 40.0 cm3 of solution. Concentration = 0.002000.0400 = 0.050 mol/dm3.
A25%[1]
Moles of CO2 = 3.024 = 0.125 mol = moles of Na2CO3. Mass = 0.125 × 106 = 13.25 g. Purity = 13.2553 × 100% = 25%.
C90.0%[1]
Moles of SO2 = 43.224 = 1.80 mol = moles of ZnS. Mass of ZnS = 1.80 × 97 = 174.6 g. Purity = 174.6194 × 100% = 90.0%.
CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) [2]
Volume ratio CH4 : O2 = 1 : 2. [1]
20 cm3 of CH4 needs 40 cm3 of O2, which is less than the 60 cm3 of O2 available. [1]
O2 is in excess, so CH4 is the limiting reagent. [1]
Volume of CO2 produced = 20.0 cm3 (ratio CH4 : CO2 = 1 : 1) [1]
Volume of O2 remaining = 60 − 40 = 20.0 cm3, so total = 20 + 20 = 40.0 cm3 [1]
0.7 × 20 cm3 = 14.0 cm3 [1]
2HNO3 + Mg → Mg(NO3)2 + H2. Moles of nitric acid = 0.030 × 0.80 = 0.024 mol, moles of Mg = 1024 = 0.41667 mol [1]
0.024 mol of nitric acid reacts with only 0.012 mol of Mg, so Mg is in excess and nitric acid is the limiting reagent. [1]
Moles of Mg(NO3)2 = 0.012 mol, so mass = 0.012 × 148 = 1.78 g [1]
NaH + H2O → NaOH + H2 [1]
Moles of NaH = 0.2424 = 0.01 mol and moles of H2O = 1.818 = 0.1 mol [1]
1 mol of NaH reacts with 1 mol of H2O, so NaH is the limiting reactant. [1]
Moles of NaOH formed = 0.01 mol [1]
Mg(OH)2 + 2HCl → MgCl2 + 2H2O [1]
Moles of HCl = 0.0276 × 0.220 = 0.006072 mol, so moles of Mg(OH)2 = 0.006072 ÷ 2 = 0.003036 mol [1]
Concentration = 0.0030360.0250 = 0.121 mol/dm3 [1]
0.12144 × (24 + 2 × 16 + 2 × 1) = 7.04 g [1]
1 dm3 of water dissolves 7.04 g, so volume = 10.07.0435 = 1.42 dm3 [1]