Atomic Mass and Molecular Mass Quiz

What did John Dalton discover about the reaction between hydrogen and oxygen?

• Oxygen is lighter than hydrogen.

• One gram of hydrogen reacts with eight grams of oxygen to form water.

• Hydrogen is heavier than oxygen.

• Hydrogen and oxygen do not react to form water.

What was Dalton's initial belief about the composition of a water molecule?

• It was made of three hydrogen atoms and one oxygen atom.

• It was made of one hydrogen atom and one oxygen atom.

• It was made of one hydrogen atom and two oxygen atoms.

• It was made of two hydrogen atoms and one oxygen atom.

How did scientists correct Dalton's misconception about water's formula?

• By demonstrating water is H3O.

• By proving water is H2O, not HO.

• By indicating water is HO2.

• By showing water is H2O2.

Why did Dalton assign hydrogen an atomic mass of one?

• To match the atomic mass of oxygen.

• To make calculations simpler, as it is the lightest element.

• Because it was the heaviest element.

• Because it was the most abundant element.

What is the atomic mass of a nitrogen atom compared to hydrogen?

• 8 times heavier

• 16 times heavier

• 12 times heavier

• 14 times heavier

What does an element's atomic number represent?

• The number of protons and neutrons

• Its place in the periodic table

• The number of electrons

• Its weight compared to hydrogen

How did the definition of atomic mass change later?

• It was compared to an oxygen atom taken as 16.

• It was compared to a carbon atom taken as 12.

• It was compared to a hydrogen atom taken as 1.

• It was compared to a nitrogen atom taken as 14.

What is the molecular mass of water (H2O)?

• 16

• 18

• 20

• 22

How is the molecular mass of a compound determined?

• By adding the atomic numbers of its atoms

• By multiplying the atomic masses of its atoms

• By subtracting the atomic masses of its atoms

• By adding the atomic masses of its atoms

What is the molecular mass of carbon dioxide (CO2)?

• 40

• 28

• 44

• 32