Which of the following is used as a depressant in the froth flotation process for separating ZnS and PbS?

The number of moles of ${K_2}C{r_2}{O_7}$ that will be needed to react with one mole of nitrite ion in acidic solution is

0.5 grams of sodium hydroxide was treated with $12.5 \mathrm{mL}$ of $0.75 \mathrm{M}$ HCl solution. The mass of sodium hydroxide left unreacted is equal to

How many gram of ${{\rm{I}}_2}$ are present in a solution which requires 40 mL, of 0.11 N ${\rm{N}}{{\rm{a}}_2}{{\rm{S}}_2}{{\rm{O}}_3}$ to react with it, ${{\rm{S}}_2}{\rm{O}}_3^{2 - } + {{\rm{I}}_2} o {{\rm{S}}_4}{\rm{O}}_6^{2 - } + 2{{\rm{I}}^ - }?$

What mass of ${\rm{Mn}}{{\rm{O}}_2}$ is reduced by 35 mL of 0.16 $N$ oxalic acid in acidic solution? The skeleton equation is, ${\rm{Mn}}{{\rm{O}}_2} + {{\rm{H}}^ + } + {{\rm{H}}_2}{{\rm{C}}_2}{{\rm{O}}_4} o {\rm{C}}{{\rm{O}}_2} + {{\rm{H}}_2}{\rm{O}} + {\rm{M}}{{\rm{n}}^{2 + }}:$

For the reaction : ${{\rm{N}}_2} + 3{{\rm{H}}_2} o 2{\rm{N}}{{\rm{H}}_3}$ ; if ${E_1}\,and\,{E_2}$ are equivalent masses of $N{H_3}$ and ${N_2}$ respectively, then ${E_1}\, - \,{E_2}$ is :

For the reaction : ${{\rm{N}}_2} + 3{{\rm{H}}_2} o 2{\rm{N}}{{\rm{H}}_3}$ ; if ${E_1}\,and\,{E_2}$ are equivalent masses of $N{H_3}$ and ${N_2}$ respectively, then ${E_1}\, - \,{E_2}$ is :

$0.2$ g of a sample of ${{\rm{H}}_2}{{\rm{O}}_2}$ required $10$ mL of $N{\rm{KMn}}{{\rm{O}}_4}$ in a titration in the presence of ${{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}{\rm{.}}$. Purity of ${{\rm{H}}_2}{{\rm{O}}_2}$ is :

What weight of ${\rm{HN}}{{\rm{O}}_3}$ is needed to convert 5 g of iodine into iodic acid according to the reaction, ${{\rm{I}}_2} + {\rm{HN}}{{\rm{O}}_3} o {\rm{HI}}{{\rm{O}}_3} + {\rm{N}}{{\rm{O}}_2} + {{\rm{H}}_2}{\rm{O}}?$ ?

How many gram of ${{\rm{I}}_2}$ are present in a solution which requires 40 mL, of 0.11 N ${\rm{N}}{{\rm{a}}_2}{{\rm{S}}_2}{{\rm{O}}_3}$ to react with it, ${{\rm{S}}_2}{\rm{O}}_3^{2 - } + {{\rm{I}}_2} o {{\rm{S}}_4}{\rm{O}}_6^{2 - } + 2{{\rm{I}}^ - }?$

2 grams of sodium hydroxide was treated with $50 \mathrm{mL}$ of $0.75 \mathrm{M}$ HCl solution. The mass of sodium hydroxide left unreacted is equal to