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Phosphorus (III) chloride molecules are pyramidal with a bond angle less than 109.5. Explain why. (2)
Pyramidal because there are 3 bonding pairs and one lone pair of electrons on P Bond angle because lone pair-bond pair repulsion is greater than bond pair-bond pair repulsion
Calcium Nitrate decomposes in a similar way to magnesium nitrate, but needs a higher temperature. Explain in terms of the charge and size of the cations. (3)
Ca2+ has larger ionic radius So Ca2+ causes less polarisation Nitrate ion electron cloud polarised
Explain why boiling temperatures increase from chlorine to iodine. (2)
Down the group, number of electrons increases So strength of London forces increases and more energy needed to separate the molecules
Explain why zinc ions are colourless (2)
Zinc ions have a full 3d subshell So electrons cannot move between d orbitals/cannot be promoted
Explain why the first ionisation energy of magnesium is higher than that of sodium (3)
Magnesium has more protons than Sodium, greater effective nuclear charge Shielding in Magnesium the same as in Sodium Force of attraction between nucleus and outer electron is greater in Mg
Explain why different alkanes in crude oil can be separated by fractional distillation (2)
Different alkanes have different boiling temperature Because of different chain length/strength of intermolecular forces
Describe how reactions happen in catalytic converters (3)
Adsorption to catalytic surface Weakenign of bonds on catalytic surface Desorption of products
Give the steps to show have 2,4-DNPH can be used to distinguish between phenylethanone and phenylethanal (4)
Formation of yellow/orange precipitate Filter then recrystallise products Determination of melting temperature Comparison and identification from use of database