Chem in the Earth System IS4T2 Review: Stoichiometry

The molar mass of an element is equal to its...

• Atomic mass
• Atomic number
• Oxidation number
• Valence electrons

The mass of one mole of substance is called...

• molecular mass
• mole constant
• molar mass
• atomic weight

What is the molar mass of table salt (NaCl)?

• 116.886 g/mol
• 35.453 g/mol
• 22.990 g/mol
• 58.443 g/mol

What is the molar mass of NaOH?

• 40 g/mol
• 38.989 g/mol
• 23.998 g/mol
• 57.004 g/mol

What is the molar mass of CO₂?

• 12
• 16
• 32
• 44

How many particles are in a mole?

• 602
• 602 million
• 602 moles
• 6.02 x 10²³

What is the molar mass of H2O, rounded to the nearest whole number?

• 3 grams

• 12 grams

• 17 grams

• 18 grams

Answer explanation

The molar mass of hydrogen is 1. The molar mass of oxygen is 16. You were asked to find the mass of H2O, so you have to multiply the molar mass of H and then multiply by the number of hydrogen atoms. Then add the molar mass of oxygen.

1 x 2 = 2 grams.

16 x 1 = 16 grams.

2 + 16 = 18 grams.

What is the molar mass of Al2O3, rounded to the nearest whole number?

• 48 grams

• 54 grams

• 102 grams

• 43 grams

Answer explanation

The molar mass of aluminum is 27. The molar mass of oxygen is 16. You were asked to find the mass of Al2O3, so you have to multiply the molar mass of aluminum and then multiply by the number of aluminum atoms. Repeat for oxygen, then add your totals.

___C₃H₈ +___O₂ --> ___CO₂ + ___H₂O

• 1,5,3,4
• 2,10,6,8
• already balanced
• 1,5,5,4

__Al + __Fe₃N₂ -->__AlN + __Fe

• already balanced
• 4,2,4,6
• 2,1,2,3
• 1,2,1,3