JAMB - Chemistry (1999 - No. 29)
Chlorine, bromine and iodine resemble one another in that they?
dissolve in alkalis
react violently with hydrogen without heating
are liquids
displace one another from solutions of their salts
Selitys
Chlorine and hydrogen do not react vigorously without heating unless exposed to sunlight or a flame. The reaction is spontaneous and explosive when exposed to these conditions. However, chlorine, bromine, and iodine all dissolve in alkali to form alkali metal halides.
Alkali metals are electropositive elements that bond ionically with halogens, which are electronegative elements.