What is the empirical formula of a compound that contains 40 percent carbon, 6.7 percent hydrogen, and 53.3 percent oxygen by mass?

40.0 g C * 1 mol C/ 12.0 g C = 3.333 mol C

6.7 g H * 1 mol H/ 1.008 g H= 6.6 mol H

53.3 g O * 1 mol/ 16.0 g O= 3.331 mol O

divide by the least moles

3.333 mol C / 3.331 = 1

6.6 mol H/ 3.331 = 1.98 ~ 2

3.331 mol O/ 3.331 = 1

empirical formula is H2CO

quartz

explanation:

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6