(a) Write an equation to show the action of strong heat on: (i) potassium trioxonitrate (V): (ii) sucrose. (b) State two observations in respect of the reac...

Assessment: WAEC SSCE - Chemistry - 1994 (Essay) Subject: Chemistry

Question 1 Report

(a) Write an equation to show the action of strong heat on:

(i) potassium trioxonitrate (V):

(ii) sucrose.

(b) State two observations in respect of the reaction between granulated zinc and dilute tetraoxosulphate (VI) acid.

Answer Details

(a) Action of strong heat

(i) Potassium trioxonitrate(V) (potassium nitrate) decomposes to the nitrite and oxygen:

\[ 2KNO_3 \to 2KNO_2 + O_2 \]

(ii) Sucrose chars (is dehydrated) to carbon and water vapour:

\[ C_{12}H_{22}O_{11} \to 12C + 11H_2O \]

(b) Granulated zinc with dilute tetraoxosulphate(VI) acid

  • Effervescence occurs as bubbles of a colourless gas (hydrogen) are given off and the zinc gradually dissolves/gets smaller.
  • The mixture warms up (the reaction is exothermic), leaving a colourless solution of zinc sulphate.

\[ Zn + H_2SO_4 \to ZnSO_4 + H_2 \]

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