SS1 CHEMISTRY

The molar mass of a substance is numerically equal to its formula mass in amu (atomic mass units). True/False

• Maybe
• True
• Sometimes
• False

In an experiment, 0.5 moles of a compound with a relative molecular mass of 80 u are used. What is the total mass of the compound used?

• a) 40 g

• b) 60 g

• c) 80 g

• d) 100 g

What is the relative molecular mass of methane (CH₄)?

• a) 16

• b) 18

• c) 20

• d) 22

Which isotope of hydrogen (¹H, ²H, or ³H) contributes the most to the average atomic mass of hydrogen in naturally occurring samples?

• a) 1H

• b) 2H

• c) 3H

• d) None of the above

Which of the following statements is NOT true about a mole?

• a) It contains approximately 6.022 × 10^23 particles.

• b) It is a unit of measurement for the amount of a substance.

• c) It can be used for any type of particle, including atoms, molecules, and ions.

• d) It is always equal to 12 grams of carbon-12.

A molecule contains 5 carbon atoms, 8 hydrogen atoms, and 2 chlorine atoms. What is its relative molecular mass?

• a) 109

• b) 119

• c) 129

• d) 139

The compound X₂O₃ contains two unknown elements X and O. If the relative molecular mass of X₂O₃ is 102 u, what is the relative atomic mass of element X?

• a) 22

• b) 24

• c) 27

• d) 28

A compound is found to contain 48.6% carbon, 6.2% hydrogen, and 45.2% oxygen by mass. What is the simplest possible molecular formula for this compound?

• a) CH₂O

• b) C₂H₄O

• c) CH₃O₂

• d) C₄H₈O₂

You need 3 moles of hydrogen gas for an experiment. Which of the following quantities corresponds to this amount?

• a) 24 g of H2

• b) 6.022 × 10^23 molecules of H2

• c) 32 cm3 of H2 at STP (standard temperature and pressure)

• d) All of the above

Which of the following molecules has the highest relative molecular mass?

• a) CO₂

• b) NH₃

• c) H₂O

• d) He