can you help me pls

Question 3(0.5) : Is PCl3 an ionic or a pure covalent compound? Data: Z(P)=15,Z(Cl)=17 What is the main interaction that ensures the cohesion of this liquid at room temperature? Question 4(0.25) : Between CH4 and CH3Br, which Van der Waals interaction does not develop? Check the box: a) Keesom b) Debye c) London Question 5(0.75) : Justify that the boiling point of CCl4(0) is 77C, while the one of CBr4(0) is 190C. Data: Z(Br)=35,Z(Cl)=17 (in the periodic table, Br is just bellow Cl ). Your explanation must contain the following facts: - the type of bonds inside the compounds: - the type of compounds (ionic, polar, non polar...) according to their qeometry : - the main interaction that links such compounds together : - the parameter that affects the strength of this interaction and the relation between this strength and the boiling point