Calculate the amount of water $(g)$ produced by the combustion of $16 \ g$ of methane. (in $g$)

$A$ $1.85 \ g$ sample of an arsenic containing pesticide was chemically converted to $AsO_4^{3-}$ (atomic mass of $As = 74.9$) and titrated with $Pb^{2+}$ to form $Pb_3(AsO_4)_2$. If $20 \ mL$ of $0.1 \ M \ Pb^{2+}$ is required to reach the equivalence point,the mass percentage of arsenic in the pesticide sample is closest to

What volume of $2 \,M \,H_2SO_4$ is required to prepare $100 \,mL$ of $0.2 \,N \,H_2SO_4$ solution (in $\,mL$)?

What is the value of percent atom economy if the molar mass of reactants is $36 \ u$ and the mass of the desired product is $27 \ u$ (in $\%$)?

If $1$ mole of $N_2$ occupies a volume of $22.4 \, L$ at $NTP$,what is the density of $N_2$ in $g/L$?

If the concentration of compound $AB_5$ is $10^{-3} \text{ mol/L}$,then the concentration of $B^{-}$ will be .......