(a) List two industrial uses of concentrated tetraoxosulphate (VI) acid (b) The diagram below represents the set-up for the electrolysis of dilute tetraoxos...
Question 1 Report
(a) List two industrial uses of concentrated tetraoxosulphate (VI) acid
(b) The diagram below represents the set-up for the electrolysis of dilute tetraoxosulphate (VI) acid. Use it to answer Questions (i) to (iii).
(i) Which letter on the diagram represents the battery?
(ii) Write an equation for the reaction occurring at the cathode
(iii) What product does V represent?
Answer Details
(a) Two industrial uses of concentrated tetraoxosulphate(VI) acid
- Manufacture of fertilizers such as ammonium tetraoxosulphate(VI) and calcium superphosphate.
- As the electrolyte in lead-acid accumulators (car batteries); also used in petroleum refining, and in the production of detergents, paints and dyes.
(b) Electrolysis of dilute tetraoxosulphate(VI) acid
Reading the set-up: the zig-zag component S is the rheostat (variable resistor), R is the cell drawn as two parallel plates, and T is the switch (key). The two inverted tubes V and U collect the gases given off at electrodes P and Q, which dip into the dilute H2SO4.
(i) The letter that represents the battery (cell) is R.
(ii) Reaction at the cathode. At the cathode, hydrogen ions are discharged (reduced) in preference to the poorly discharged tetraoxosulphate(VI) ions:
\[ 2H^{+}_{(aq)} + 2e^{-} \rightarrow H_{2(g)} \]
(iii) Product V. V is collected at the electrode joined to the negative terminal, i.e. the cathode, so V represents hydrogen gas. It is the more abundant gas: for every 1 volume of oxygen liberated at the anode, 2 volumes of hydrogen are collected here, since
\[ 2H_2O_{(l)} \rightarrow 2H_{2(g)} + O_{2(g)} \]
(overall) gives twice as much hydrogen as oxygen.
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