The mole and the Avogadro constant

How many ions are present in 142 g of $\ce{Na2SO4}$? $M(\ce{Na2SO4}) = 142\ \mathrm{g\,mol^{-1}}$ A. 1 B. 3 C. $6.02 \times 10^{23}$ D. $1.81 \times 10^{24}$

What is the number of hydrogen atoms in 0.0500 mol of hydrated magnesium sulfate, $\ce{MgSO4 * 7H2O}$? A. $3.01 \times 10^{22}$ B. $4.21 \times 10^{23}$ C. $2.11 \times 10^{23}$ D. $4.21 \times 10^{22}$

A total charge of 1500.0 C flows through the external circuit during one discharge of the battery. Determine how many sodium ions are released at the anode. Use section 2 of the data booklet.

4.81 g of sulfur was heated in a stream of chlorine gas until the reaction was complete. The mass of the chloride produced was 10.13 g. (i) Calculate how many atoms are present in this 4.81 g sample of sulfur. Use sections 2 and 7 of the data booklet. (ii)…

What is the total number of ions in 0.30 mol of iron(III) nitrate, $\ce{Fe(NO3)3}$? A. $0.30 \times 1 \times 6.02 \times 10^{23}$ B. $0.30 \times 3 \times 6.02 \times 10^{23}$ C. $0.30 \times 4 \times 6.02 \times 10^{23}$ D.…

A cylinder contains 80 g of argon and 12.0 g of helium. What is the ratio of the number of argon atoms to the number of helium atoms in the cylinder? A. 0.15 B. 0.67 C. 1.5 D. 6.7