A student investigates an aqueous solution of an unknown potassium halide, KX\text{KX}KX:
Which of the following correctly describes the expected observation for the reaction with chlorine gas, and the correct trend and explanation for the electronegativity of the elements down Group 7?
An orange-brown solution is formed; electronegativity decreases down Group 7 because atomic radius and shielding increase.
A yellow-green solution is formed; electronegativity increases down Group 7 because the nuclear charge increases.
A dark-grey precipitate is formed; electronegativity decreases down Group 7 because the outer electrons are closer to the nucleus.
An orange-brown solution is formed; electronegativity increases down Group 7 because the electrostatic attraction to the bonding pair of electrons becomes stronger.
106 exam-style questions on Edexcel GCSE Chemistry 7.2 Group 7, covering 7.2.1 Physical properties of the halogens, 7.2.2 Reactions of the halogens, 7.2.3 Relative reactivity and displacement reactions of the halogens, and 7.2.4 Halogen displacement as a redox reaction. Each one has a worked solution and a mark scheme showing where the marks go.