Question

Consider the reactions shown below :

Which of the following statements is false?
[Atomic mass of zinc $= 65.4$]

• A. Silver chromate has the formula $Ag _{2} CrO _{4}$.
• B. The minimum mass of zinc required to reduce $0.100\, mole$ of $Cr ^{3+}$ to $Cr ^{2+}$ is $6.54\, g$
• C. The conversion of $CrO _{4}^{2-}$ into $Cr _{2} O _{7}{ }^{2-}$ is not a redox reaction.
• D. The equation, $Cr _{2} O _{7}^{2-}+14 H ^{+}+6 Fe ^{2+} \rightarrow 6 Fe ^{3+}+2 Cr ^{3+}+7 H _{2} O$ correctly describes the reduction of $Cr _{2} O _{7}^{2-}$ by acidified $FeSO _{4}$

Answer 1

Answer: (B)

(a) Formula of silver chromate will be $Ag _{2} CrO _{4}$

(b) Minimum mass of zinc required for reduction of 0.1 mole of $Cr ^{3+} \text { to } Cr ^{2+} $

$=\frac{0.1}{2} \text { moles of } Zn =\frac{6.54}{2} g =3.27 \,g$

(c) $CrO _{4}^{2-} \rightleftharpoons Cr _{2} O _{7}^{2-}$

in both ions chromium is in $+6$ state.

(d) Given reaction is correct.