EDEXCEL A LEVEL 2023 CHEMISTRY

(ii) Explain which of chromium or calcium most easily forms a +2 ion using all of the data in the table. - correct answersCalcium forms 2+ more readily as the sum of 1 and 2 ionisation energies are lower Calcium has a lower nucleur charge So less attraction between outer electrons and nucleus (ii) Give a reason why the silver nitrate must be acidified. 1 - correct answersTo remove the carbonate ions 2 Chemists often use the term 'orbital' when considering atomic structure. (a) State what is meant by the term orbital. (2) - correct answersa region / space (in an atom) in which there is a high probability of finding electron(s) / electron(s) are (most) likely to be found • containing (a maximum of ) 2 / a pair of electrons (with opposite spin) (1) Another silver compound is silver chloride, AgCl. Values for its lattice energy can be found by experiment or by theoretical calculation. (i) Give two assumptions used in the model to calculate the theoretical lattice energy. (2) Compound Experimental lattice energy / kJ mol-1 Theoretical lattice energy / kJ mol-1 Silver chloride -905 -833 - correct answersCharge is evenly distributed Ions are spherical and purely ionic b) The ionic salts sodium benzoate and potassium benzoate are both used as food preservatives. Explain why the melting temperature of sodium benzoate is higher than the melting temperature of potassium benzoate. (2) - correct answersSnakes ionic radii same charge so stronger ionic bonding so more energy needed to break bknds Chemists can test for the presence of bromide ions in solution by adding a small amount of acidified silver nitrate solution. The solubility of the precipitate in aqueous ammonia is then tested