During the estimation of oxalic acid $V/S$ $KMnO_4$,the self-indicator is:

While titrating a dilute $HCl$ solution with an aqueous $NaOH$ solution,which of the following will not be required?

$A$ solution containing $Na_2CO_3$ and $NaOH$ requires $300 \ mL$ of $0.1 \ N$ $HCl$ using phenolphthalein as an indicator. Methyl orange is then added to the above titrated solution when a further $25 \ mL$ of $0.2 \ N$ $HCl$ is required. The amount of $NaOH$ present in the solution is ................. $g$ $(NaOH = 40, Na_2CO_3 = 106)$.

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:

Temporary hardness in tap water is measured in terms of parts of $CaCO_3$ per $10^6$ parts of water. If $500 \ mL$ of hard water containing $Ca(HCO_3)_2$ was titrated against $\frac{1}{20} \ M \ H_2SO_4$ solution in the presence of a methyl orange indicator,and it required $40 \ mL$ of titrant,then the temporary hardness in the tap water is .............. $ppm$.

$3.92 \, g$ of ferrous ammonium sulfate crystals are dissolved in $100 \, mL$ of water. During titration,$20 \, mL$ of this solution is required for complete oxidation by $18 \, mL$ of $KMnO_4$ solution. Calculate the weight of $KMnO_4$ in $1 \, L$ of the solution in grams.