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Chem unit 1 pastpap

QuestionAnswer
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.
Created by: ufuoma
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