# When a silvery grey powder of a solid (A) is mixed with a powder of solid (B) no reaction occurs.

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When a silvery grey powder of a solid (A) is mixed with a powder of solid (B) no reaction occurs. But if the mixture is ignited and lighted using magnesium ribbon a reaction occurs with evolution of large amount of heat forming product (C) which settles down as liquid metal and the solid product (D) formed floats on the liquid (C). (C) in solid form reacts with moisture to form rust. The amount of heat generated during the reaction is so high that the reaction is used in welding of electric conductors, joints in railway tracks. Based on this information, answer the following questions.

(I) Identify (A), (B), (C) and (D).

(II) Write the balanced chemical equation for the reaction. Name the type of reaction.

(III) If (A) reacts with air on heating what will be the nature of oxide formed ?

(IV) Does oxide of (A) react with aqueous NaOH and/or HCI . Give balance chemical equation/s.

## 1 Answer

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(I) A = AI

B = Fe2O3

C = Fe

D = Al2O3 (III) 2Al + 3O2 → 2Al2O3

When (A) reacts with air, it will give aluminium oxide which is amphoteric in nature.

(IV) Al2O3 + 6HCl(aq) → 2AlCl3 + 3H2O

Al2O3 + 2NaOH(aq) → 2NaAlO2 + H2O

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