Which of the reactions below will spontaneously take place?
1. copper + iron sulphate
2. magnesium + zinc chloride
3. lead + aluminium chloride
4. calcium + sodium chloride
2. magnesium + zinc chloride
To determine which of the reactions will spontaneously take place, we need to refer to the reactivity series of metals. The reactivity series arranges metals in order of their reactivity, with the most reactive metals at the top and the least reactive metals at the bottom.
The reactivity series is as follows:
Potassium (K)
Sodium (Na)
Calcium (Ca)
Magnesium (Mg)
Aluminium (Al)
Zinc (Zn)
Iron (Fe)
Lead (Pb)
Copper (Cu)
Silver (Ag)
Gold (Au)
According to the reactivity series, a metal will react with the salt of a metal located below it on the list. This means that a metal higher in the reactivity series can replace a metal lower in the reactivity series in a compound.
Based on the given reactions, let's evaluate each reaction in terms of the reactivity series:
1. copper + iron sulphate:
Copper (Cu) is below iron (Fe) in the reactivity series, so copper cannot displace iron from iron sulphate. This reaction will not spontaneously take place.
2. magnesium + zinc chloride:
Magnesium (Mg) is above zinc (Zn) in the reactivity series, so magnesium can displace zinc from zinc chloride. This reaction will spontaneously take place.
3. lead + aluminium chloride:
Lead (Pb) is below aluminium (Al) in the reactivity series, so lead cannot displace aluminium from aluminium chloride. This reaction will not spontaneously take place.
4. calcium + sodium chloride:
Calcium (Ca) is below sodium (Na) in the reactivity series, so calcium cannot displace sodium from sodium chloride. This reaction will not spontaneously take place.
Therefore, the only reaction that will spontaneously take place among the given options is magnesium + zinc chloride.