IB Chemistry S1.4 Counting Particles by Mass: the Mole Questionbank

What is the number of atoms in 1.00 mol of helium gas?

A marine biologist studies the effect of ocean acidification on calcium carbonate shells. In the lab, she reacts powdered $\mathrm{CaCO_3}$ with excess hydrochloric acid and collects the carbon dioxide gas evolved. The reaction is:

$\mathrm{CaCO_3(s)} + 2\mathrm{HCl(aq)} \to \mathrm{CaCl_2(aq)} + \mathrm{H_2O(l)} + \mathrm{CO_2(g)}$

She starts with a $1.25\ \mathrm{g}$ sample of $\mathrm{CaCO_3}$ and the gas collected has a volume of $240\ \mathrm{cm^3}$ at room temperature and pressure (RTP, for gas molar volume).

A 1.00 g sample of a metal $M$ reacts with excess oxygen to form 1.27 g of the oxide $M_2O$. What is the relative atomic mass ($$) of ?

Which unit is commonly used for molar mass?

How many molecules are there in 2.00 mol of carbon dioxide?