If $25 \ mL$ of $H_2SO_4$ solution is neutralized by $32.63 \ mL$ of $0.164 \ M \ NaOH$ solution,what is the molarity of the $H_2SO_4$ solution?

In a titration experiment,$10 \, mL$ of an $FeCl_{2}$ solution consumed $25 \, mL$ of a standard $K_{2}Cr_{2}O_{7}$ solution to reach the equivalence point. The standard $K_{2}Cr_{2}O_{7}$ solution is prepared by dissolving $1.225 \, g$ of $K_{2}Cr_{2}O_{7}$ in $250 \, mL$ water. The concentration of the $FeCl_{2}$ solution is closest to $..... \, N$
[Given : molecular weight of $K_{2}Cr_{2}O_{7} = 294 \, g \, mol^{-1}$]

$20 \, mL$ of calcium hydroxide was consumed when it was reacted with $10 \, mL$ of an unknown solution of $H_2SO_4$. Also,$20 \, mL$ of a standard solution of $0.5 \, M$ $HCl$ containing $2$ drops of phenolphthalein was titrated with calcium hydroxide. The mixture showed a pink color when the burette displayed the value of $35.5 \, mL$,whereas the burette showed $25.5 \, mL$ initially. The concentration of $H_2SO_4$ is $..........M$ (Nearest integer).

$3.92 \, g$ of ferrous ammonium sulphate crystals are dissolved in $100 \, mL$ of water. $20 \, mL$ of this solution requires $18 \, mL$ of $KMnO_4$ during titration for complete oxidation. The weight of $KMnO_4$ present in one litre of the solution is ............. $g$.

Solution $X$ contains $Na_2CO_3$ and $NaHCO_3$. $20 \ mL$ of $X$ when titrated using methyl orange indicator consumed $60 \ mL$ of $0.1 \ M \ HCl$ solution. In another experiment,$20 \ mL$ of $X$ solution when titrated using phenolphthalein consumed $20 \ mL$ of $0.1 \ M \ HCl$ solution. The concentrations (in $mol \ L^{-1}$) of $Na_2CO_3$ and $NaHCO_3$ in $X$ are respectively:

Phenolphthalein is used as an indicator for the titration of sodium hydroxide solution against a standard solution of oxalic acid. The colour change that is observed at an alkaline pH close to the equivalence point during this titration is: