The mountain · Science ridge · camp 2 of 4
Chemistry
Chemistry: particles and states, atoms and the periodic table, reactions and equations, acids and bases, rates and energy changes.
Walk to this camp
Three questions light the next lantern. Nothing to install, no sign-up.
Eight rungs, one trail
Every camp on the mountain has the same eight rungs: the eight altitudes Alpenrise measures, read back in the words of your own school system. Rung 1 is the bottom of secondary school; rung 8 is beyond the final exam.
| Rung | New Zealand | United Kingdom | Cambridge | IB |
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| R1Explorer | Year 7 | Year 7 | Stage 7 | MYP 1 |
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| R2Pathfinder | Year 8 | Year 8 | Stage 8 | MYP 2 |
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| R3Voyager | Year 9 | Year 9 | Stage 9 | MYP 3 |
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| R4Navigator | Year 10 | Year 10 · GCSE yr 1 | IGCSE Yr 1 | MYP 4 |
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| R5Pioneer | Year 11 | Year 11 · GCSE | IGCSE Yr 2 | MYP 5 |
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| R6Summit | Year 12 | Year 12 · AS | AS Level | DP 1 |
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| R7Apex | Year 13 | Year 13 · A Level | A Level | DP 2 |
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| R8Beyond | NZ Scholarship | beyond A Level | STEP prep | DP HL+ |
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One question from each rung
The mountain draws three questions per rung from the same slice as the free placement. Here is one from each rung of Chemistry, shown without its answer.
- Rung 1 · Explorer · Year 74 g of sugar is dissolved in water to make 200 mL of drink. How many grams of sugar are there in every 100 mL?
- Rung 2 · Pathfinder · Year 8A green liquid has been squeezed out of crushed leaves. Suggest how to show that more than one coloured pigment is present, and give a reason for your answer.filtration, because the solid does not dissolve in the liquid at all · evaporation, because the solid is left behind when the water is gone · simple distillation, because the liquid boils off and is then cooled · chromatography, because the coloured dyes travel at different speeds
- Rung 3 · Voyager · Year 9Leah needs to control the concentration of the acid, across six separate runs. Outline how she should actually do it — choose the step that holds that value the same from run to run, rather than one that only looks as though it does.Make up all of the acid needed in one large batch, and pour every run from that batch. · Open a fresh bottle of acid for each run, so that none of it has stood around. · Measure 50 cm³ of acid with the same measuring cylinder for every single one of the runs. · Copy the concentration printed on the bottle into the results table each time.
- Rung 4 · Navigator · Year 10Using the rounded atomic masses given, what percentage of the mass of iron oxide, Fe₂O₃ (Fe=56, O=16) comes from iron?
- Rung 5 · Pioneer · Year 11Reactivity series, most reactive first: potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, copper, silver.
A metal can push a less reactive metal out of a compound in solution; a less reactive metal cannot.
Which one of these mixtures will react?Aluminium added to copper(II) sulfate solution · Copper added to aluminium sulfate solution · Lead added to zinc sulfate solution · Silver added to iron(II) sulfate solution
- Rung 6 · Summit · Year 12Bond energies (kJ/mol): N≡N = 945, N=O = 631, O=O = 498.
ΔH = (energy needed to break all the bonds in the reactants) − (energy given out when all the bonds in the products form).
N₂ + O₂ → 2NO
N₂ has one N≡N bond, O₂ has one O=O bond, and each NO has one N=O bond.
Calculate ΔH for this reaction, in kJ/mol. Give the sign as well as the number.
- Rung 7 · Apex · Year 13A sample of a compound contains 36 g of carbon (Ar = 12), 18 g of hydrogen (Ar = 1) and 96 g of oxygen (Ar = 16). Work out its empirical formula, then give the relative formula mass of that empirical formula.
- Rung 8 · Beyond · NZ Scholarship2Mg + O₂ → 2MgO
A chemist reacts 4.8 g of magnesium (Mg, M = 24 g/mol) and 6.4 g of oxygen (O₂, M = 32 g/mol). M(MgO) = 40 g/mol.
The reaction actually produces 7 g of magnesium oxide.
What is the percentage yield?
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