How many moles are equivalent to $5.6 \ L$ of oxygen gas at $NTP$?

$A$ quantity of aluminium has a mass of $54.0 \ g$. What is the mass of the same number of magnesium atoms? ........... $g$

Two flasks $A$ and $B$ of $500 \ mL$ each are filled with $O_2$ and $SO_2$ respectively at $300 \ K$ and $1 \ atm$ pressure. Then the flasks contain:

How many $H$ atoms are present in $0.46 \, g$ of ethanol $[C_2H_5OH]$?

How many $H$ atoms are present in $0.046 \ g$ of ethanol $(C_2H_5OH)$?

If $10^{21}$ molecules are removed from $200 \ mg$ of $CO_2$,how many moles of $CO_2$ will remain?