How many moles are present in 32g of oxygen gas ($O_2$)? (Atomic mass of O = 16u)

Millimole of a solute in a solution can be given by :

A sample of chalk containing 75% $\mathrm{CaCO_3}$ by mass is heated. If 15 g of $\mathrm{CO_2}$ is produced, what was the initial mass of the chalk sample? (Atomic mass of $\mathrm{Ca} = 40$)

$\left[\mathrm{CaCO_3} \stackrel{\Delta}{\longrightarrow} \mathrm{CaO} + \mathrm{CO_2}\right]$

A 1.00 g sample containing $BaCl_2\cdot2H_2O$ is heated to a constant mass of 0.835 g. What was the mass percent of barium in the original sample?

Upon heating 20 g of limestone with 20% purity, what mass of $\mathrm{CO_2}$ is produced? (Atomic mass of $\mathrm{Ca} = 40$)

$\left[\mathrm{CaCO_3} \stackrel{1200 \mathrm{K}}{\longrightarrow} \mathrm{CaO} + \mathrm{CO_2}\right]$

25 mL of a mixture of $NaOH$ and $Na_2CO_3$ solution requires 20 mL of 0.5 N $HCl$ using phenolphthalein as an indicator. Another 25 mL of the same mixture requires 30 mL of the same $HCl$ solution when methyl orange is used as an indicator. Calculate the ratio of normalities of $NaOH$ and $Na_2CO_3$ in the mixture.

What weight of ${\rm{FeS}}{{\rm{O}}_4}$ (mol. wt. =152) will be oxidised by 200 mL of normal ${\rm{KMn}}{{\rm{O}}_4}$ solution in acidic solution?

Volume of $C{O_2}$ produced on heating 10 g of limestone at S.T.P

How many milliliter of 0.5 $N$ ${\rm{SnC}}{{\rm{l}}_2}$ solution will reduce 600 mL of 0.1 $N$ ${\rm{HgC}}{{\rm{l}}_2}$ to ${\rm{H}}{{\rm{g}}_2}{\rm{C}}{{\rm{l}}_2}$?

How many moles of $CO_2$ are produced when 2 moles of propane ($C_3H_8$) are completely combusted in excess oxygen?

2 mole of ${\rm{FeS}}{{\rm{O}}_4}$ are oxidized by 'X' mole of ${\rm{KMn}}{{\rm{O}}_4}$ whereas 2 mole of ${\rm{Fe}}{{\rm{C}}_2}{{\rm{O}}_4}$ are oxidized by 'Y' mole of ${\rm{KMn}}{{\rm{O}}_4}$. The ration f 'X' and 'Y' is :