Question

What volume of ​$0.1M,KMn{O_4}$ is needed to oxidize $5mg$ of ferrous oxalate in acidic medium? (Molecular weight of ferrous oxalate is$144g/mol$)
A.$0.20ml$
B.$0.1ml$
C.$0.4ml$
D.$2.08ml$

Answer 1

One mole needs $5$ moles of electrons in an acidic medium to reduce to. To find the volume of $0.1{\text{ }}M$solution, which contains the required $0.4167$ moles.

Complete step by step answer:
Milliequivalents of $KMn{O_4} = V \times 0.1 \times 5$
Milliequivalents of $Fe{({C_2}{O_4})_2} = \dfrac{{Weight(g)}}{{Ew}} \times 1000$
$F{e^{ + 2}} \to F{e^{ + 3}} + {e^ - }$
${C_2}O_4^{2 - } \to 2C{O_2} + 2{e^ - }$
(n = 3)
Equivalent weight of $Fe({C_2}{O_4}) = \dfrac{{Mw}}{3} = \dfrac{{144}}{3}$
Milliequivalents of $Fe({C_2}{O_4}) = \dfrac{{5 \times {{10}^{ - 3}}}}{{\dfrac{{144}}{3}}} \times {10^3} = \dfrac{{5 \times 3}}{{144}}$
Milliequivalents of $KMn{O_4} =$ Milliequivalents of $Fe({C_2}{O_4})$
$\therefore V \times 0.1 \times 5 = \dfrac{{5 \times 3}}{{144}}$
$\therefore V = 0.20ml$
An equivalent (symbol: officially equivalent; unofficially but often Eq) is the amount of a substance that is (or is equivalent to) an arbitrary quantity of another substance in a given chemical reaction. It is an archaic unit of measurement that was used in chemistry and biological sciences (see equivalent weighting in history). An equivalent mass is called its equivalent weight. In a more formal definition, the equivalent is the amount of substance required to do any of the following: reacting with or supplying one mole of hydrogen ions (${H^ + }$ ) in an acid-base reaction or supplying one mole of electron redox reaction.
According to this definition, the number of moles of an ion in a solution is equal to one, multiplied by the validity of that ion. If $1$ mole of $NaCl$ and $1$ mole of $CaC{l_2}$ dissolve in the solution, that solution contains $1$ equiv Na, $2$ equiv Ca, and $3$ equ $Cl$. (Calcium has a validity of $2$ , so the ion is equivalent to $1$ mole $2$.)

Note:
An earlier definition, used exclusively for chemical elements, holds that an equivalent is the amount of a substance that is 1 gram (0.035 oz) of hydrogen, 16 grams (0.56 oz), or 35.5 grams (1.25 oz) Will react with. Chlorine - or that will displace any of the three.