Question Topics: Structure 1.4 Counting particles by mass: The mole

What is a possible empirical formula for a substance with \( M_r = 58 \)? I. \( C_2H_5 \) II.

How many oxygen atoms are present in \( 0.0200 \, mol \) of \( CuSO_4 \cdot 5H_2O \)?

What is the empirical formula of a compound with the following composition by mass? \( C=37.5\% \) \( H=12.5\% \)

How many ions are present in 0.20 mol of \( (NH_{4})_{2}SO_{4} \)?

$5.72~g$ of $Na_{2}CO_{3} \cdot 10H_{2}O$ ($M_{r}=286~g\cdot mol^{-1}$) is dissolved in water to prepare $0.4~dm^{3}$ of aqueous solution. What is the