The molar mass of oxygen atoms is 16 g/mol. What is the mass of 0.25 moles of oxygen atoms?

What is the mass of 0.2 moles of oxygen atoms?

Rank the following samples from least to greatest number of atoms:

I. 5 g of $H_2$

II. 5 g of $O_2$

III. 5 g of $N_2$

IV. 5 g of $Cl_2$

Which of the following statement is correct

Which of the following contains the largest number of water molecules?

0.3 g of an oxalate salt was dissolved in 100 mL solution. The solution required 90 mL of $N/20$ ${\rm{KMn}}{{\rm{O}}_4}$ for complete oxidation. The % of oxalate ion in salt is:

A student heats 40.0 g of a mixture containing magnesium carbonate and some inert impurities. Upon complete decomposition, 8.0 g of magnesium oxide is formed. Calculate the percentage by mass of magnesium carbonate in the original mixture. (Atomic weight: $Mg = 24$)

A 20 L vessel contains 0.1 mole of $O_2$ at 300 K. $O_3$ is prepared in the vessel by subjecting $O_2$ to silent electric discharge till the volume is reduced to 15 L at 300K. What is the number of moles of $O_3$ formed?

13.5 g aluminium changes to ${\rm{A}}{{\rm{l}}^{3 + }}ion$ in solution by losing :

Which of the following contains the greatest number of helium atoms?

Which sample contains the largest number of helium atoms?