Question | Answer |
Which of the following bond angles occur in a molecule of ethanol, C2H5OH? | 104.5° and 109.5. |
Which of the following molecules is linear | Carbon dioxide, CO2. |
Chlorine has two isotopes with relative isotopic mass 35 and 37. Four m/z values are given below. Which will occur in a mass spectrum of chlorine gas, Cl2, from an ion with a single positive charge? | 72 |
The Avogadro constant is 6.02 × 1023 mol–1. | 0 025/126 9 x 6.02 102 |
Which equation represents the reaction for which the enthalpy change is the standard enthalpy change of formation, ΔHf○, of sodium nitrate, NaNO3? | Na(s) + ½N2(g) + 1½O2(g) NaNO3(s). |
Which equation represents the reaction for which the enthalpy change, ΔH, is the mean bond enthalpy of the C–H bond? | 1/4CH4(g) -->1/4C(g) + H(g). |
orbitals from which the first five electrons are removed during ionization, starting with the first electron, are | 3p 3s 3s 2p 2p |
Going across the Periodic Table from sodium to aluminium | the melting temperature increases. |
Going down Group 1 from lithium to rubidium | the first ionization energy decreases. |
The bonding in magnesium oxide, MgO, is | ionic |
Which of the following mixtures could not form when octane, C8H18, is cracked? | heptane + ethane |
MgCl can be made by reacting solid MgCO3, with dilute HCL
Write an equation for the reaction, including state symbols | MgCO3(s) + 2HCl(aq) --> MgCl2(aq) + H2O(l) + CO2(g) |
TWO observations you would make when the reaction is taking place. | Bubbles (of gas)/ fizzing/ effervescence
Solid disappears/ disintegrates /gets smaller /dissolves OR MgCO3 disappears (if given as solid in, Mixture gets warmer/cooler OR temperature change occurs/ heat change occurs |
Suggest why slightly more than this mass of magnesium carbonate is used in practice. | To ensure all acid reacts/ all acid is used up / to ensure product is neutral/ it (HCl) is neutralised |
How would you separate the magnesium chloride solution from the reaction mixture in (iii)? | Filter |
Give ONE reason why the yield of crystals is less than 100%, even when pure compounds are used in the preparation. | Some stays in solution / losses on transferring from one container to another/ loss on filtering /crystals left behind/some left on filter paper |
What does this data indicate about the bonding in magnesium chloride | Not 100% ionic /almost completely ionic
OR (partial) covalent character/ almost no covalency OR Discrepancy in BH values indicates polarisation (of ions) |
Explain why there is a greater difference between the experimental (Born-Haber) and theoretical lattice energies for magnesium iodide, MgI2, compared with magnesium chloride. | I- larger (than Cl-) (1) so (ion) easier to polarise /distort (1) increases covalent character / more covalent than MgCl2 / converse for MgCl2 / description of polarisation instead of the term |
ppm | parts per million |
Magnesium chloride can be used as a supplement in the diet to treat patients with low amounts of magnesium in the blood. Suggest ONE property which makes it more suitable for this purpose than magnesium carbonate. | (More) soluble (in water)/ (more) soluble in blood stream/ can be given as solution/ won’t produce gas in stomach / won’t react with stomach acid |
MgCl2.6H2O, which have molar mass 203.3 g mol–1, was obtained.
Calculate the percentage yield of this reaction. | 100% yield = (203.3 x 0.025) /5.08(25)g) yield = (3.75 x 100) = 74 % |
Write an ionic equation for the reaction of hydrogen ions with carbonate ions. State symbols are not required. | 2H+ + CO3 2- ® H2O + CO2 |
Suggest ONE reason why sulphuric acid is considered less hazardous than hydrochloric acid as a descaler. | Less easy to spill solid (in storage) OR doesn’t spread if spilt OR easy to sweep up if spilt OR less corrosive/
less strongly acidic than HCl. |