MCQ
${K_2}C{r_2}{O_7}$ on heating with aqueous $NaOH$ gives
- ✓$CrO_4^{2 - }$
- B$Cr{(OH)_3}$
- C$C{r_2}O_7^{2 - }$
- D$Cr{(OH)_2}$
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$Pt(s) |H_2(g)\,|\,HCOOH(aq.)\,||\,CH_3COOH(aq.)\,|\,H_2(g)|Pt(s)$
at $25\,^o C$ is ............ $\mathrm{V}$
$(K_a$ of $HCOOH \,= 2.4 × 10^{-4}$ , $K_a$ of $CH_3COOH = 1.8 × 10^{-5}$ , $log\,2\, = 0.3,\, log \,0.48, \frac{2.303 \times 298 \times R}{F} = 0.06)$
$(a)\ Pb^{+2} > Pb^{+4} , Tl^{+1} < Tl^{+3}$
$(b)\ Bi^{+3} < Sb^{+3 }, Sn^{+2} < Sn^{+4}$
$(c)\ Pb^{+2} > Pb^{+4} , Bi^{+3} > Bi^{+5}$
$(d)\ Tl^{+3} < In^{+3} , Sn^{+2} > Sn^{+4}$
$(e)\ Sn^{+24} < Pb^{+2} , Sn^{+4} > Pb^{+4}$
$(f)\ Sn^{+2} < Pb^{+2} , Sn^{+4} < Pb^{+4}$

| list $I$ (species) | list $II$ ( $O-N-O$ angle) |
| $(A)$ $NO_2^+$ | $(1)$ $180^o$ |
| $(B)$ $NO_2$ | $(2)$ $132^o$ |
| $(C)$ $NO_2^-$ | $(3)$ $120^o$ |
| $(D)$ $NO_3^-$ | $(4)$ $115^o$ |
| $(5)$ $109^o$ |