CBSE Class 10 Science 2020 · Paper 31/5/1 · Question 15

Chemical Reactions and Equations 3 marks Medium

A shining metal ‘M’, on burning gives a dazzling white flame and changes to a white powder ‘N’.

Answer

M is magnesium and N is magnesium oxide; $2 Mg + O_{2} \to 2 MgO$ , and magnesium is oxidised because it gains oxygen.

(a) ‘M’ is magnesium (

Mg

) and ‘N’ is magnesium oxide (

MgO

). (b)

2 Mg (s) + O_{2} (g) ⟶ 2 MgO (s)

(c) ‘M’ undergoes oxidation, because magnesium gains oxygen to form magnesium oxide (equally, each magnesium atom loses two electrons,

Mg ⟶ Mg^{2 +} + 2 e^{-}

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