Which of the following metals would readily displace hydrogen from steam?

Analyze the question The question asks which metal is reactive enough to displace hydrogen from steam (water vapour). This is a question about the reactivity series.

Explain the concept Metals higher in the reactivity series react with water or steam to release hydrogen:

• K, Na, Ca react with cold water
• Mg, Al, Zn, Fe react with steam (Mg also reacts very slowly with cold water)
• Metals below hydrogen (Pb, Cu, Hg, Ag, Au) do not react with water or steam

Reactivity series (high to low): K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Ag > Au

Solution Check each option:

• A. Copper: below hydrogen, so no reaction.
• B. Lead: just above hydrogen, but it is so unreactive that it does not react with steam in any noticeable way.
• C. Magnesium: high in the series. It burns in steam with a bright white flame:

Mg(s) + H₂O(g) → MgO(s) + H₂(g)

• D. Silver: very low in the series, so no reaction.

Answer: C (Magnesium)

Exam tip Remember the order with the phrase: "Please Stop Calling Me A Zebra, I Like Her Computer Science Group" (Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Lead, Hydrogen, Copper, Silver, Gold). For steam questions, look for the metal from Mg to Fe. Here, only Magnesium qualifies.