<p>When the ion&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML" class="wrs_chemistry"><msub><mi>Cr</mi><mn>2</mn></msub><msubsup><mi mathvariant="normal">O</mi><mn>7</mn><mrow><mn>2</mn><mo>-</mo></mrow></msubsup></math>&nbsp;acts as an oxidant in acidic aqueous solution the ion&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>C</mi><msup><mi>r</mi><mrow><mn>3</mn><mo>+</mo></mrow></msup></math>&nbsp;is formed. How many mole of&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>S</mi><msup><mi>n</mi><mrow><mn>2</mn><mo>+</mo></mrow></msup></math>&nbsp;would be oxidised to&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>S</mi><msup><mi>n</mi><mn>4</mn></msup></math>&nbsp;by one of&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML" class="wrs_chemistry"><msub><mi>Cr</mi><mn>2</mn></msub><msubsup><mi mathvariant="normal">O</mi><mn>7</mn><mrow><mn>2</mn><mo>-</mo></mrow></msubsup></math>&nbsp;ions?</p>