O-LevelChemistryBonding & Structure5070/21 · May/June 2023 · Q49 Marks
This question is about compounds that contain phosphorus.
- (a)The formula for a phosphide ion can be written as 31P3-. 15 Complete Table 4.1 to show the number of particles in this phosphide ion. Table 4.1 particle number of particles electron neutron proton[3]
- (b)State why the formula for a phosphide ion is P³- rather than P2– or P4–.[1]
- (c)The formula for a calcium ion is Ca2+. Deduce the formula for calcium phosphide.[1]
- (d)Calcium phosphate, Ca3(PO4)2, is an ionic compound. Explain why calcium phosphate has a high melting point.[2]
- (e)Calculate the percentage by mass of phosphorus in calcium phosphate. Give your answer to two significant figures. percentage by mass[2]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.
- 4(a) electron 18 (1) neutron 16 (1) proton 15 (1)
- 4(b) P3- has full outer shell of electrons (1)
- 4(c) Ca3P2 (1)
- 4(d) giant structure (1) strong attraction between positive and negative ions / strong electrostatic attraction between ions (1)
- 4(e) Mr = 310 (1) % = 20% (1)
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