Topic 3 Test 2025

What is the molar mass of Cl₂?

• 17 g/mol

• 35.5 g/mo;

• 71.0 g/mol

• 89 g/mol

Calculate the molar mass of KOH.

• 28 g/mol

• 56 g/mol

• 84 g/mol

• 112 g/mol

Calculate the molar mass of Ba(C₂H₃O₂)₂

• 255.3 g/mol

• 237.3 g/mol

• 228.3 g/mol

• 196.3 g/mol

How many of each type of atom are in Ca(OH)2?

​ (a)   Ca

​ (b)   O

2 ​ (c)  

​ (d)   atoms total

• 1
• 2
• H
• 5
• 3
• OH
• Ca

Answer explanation

There is no number after the Ca, so there is one calcium. There is one O inside the parentheses, and a 2 outside the parentheses, so you multiply 1 x 2 = 2 oxygen. The same applies to the hydrogen.

1 Ca + 2 O + 2 H = 5 atoms total

Tags

NGSS.MS-PS1-1

How many of each type of atom are in Na2SO4?

​ (a)   Na

​ (b)   S

​ (c)   O

​ (d)   atoms total

• 2
• 1
• 4
• 7
• 3
• 5
• 6

Answer explanation

There is a 2 after the Na, so there are 2 Na. There is no number after the S, so there is 1 S. There is a 4 after the O, so there are 4 O.

Tags

NGSS.MS-PS1-1

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

• 6 grams

• 10 grams

• 11 grams

• 12 grams

• 13 grams

Answer explanation

The atomic mass of carbon is 12.011 (your periodic table might give a slightly different number). Look at the number immediately after the decimal. If it is a 0-4, the numbers in front of the decimal stay the same. So 12.011 rounds to 12.

If you picked 6, that is the atomic number, not the atomic mass.

Units of Molar Mass are....

• g/mol

• mol/g

• g

• mol

Tags

NGSS.HS-PS1-7

What is the mass of one mole of aluminum?

• 27 g
• 13 g
• 54 g
• 14 g

The number of particles present in one mole of H₂O molecule is

• 18.02 g/mol.

• 18.02 amu.

• 6.02 x 10²³ molecules.

• 18.02 g.

How many water molecules are in 5.2 moles of water?

• 6.0 x 10²³ molecules

• 5.2 molecules

• 3.1 x 10²⁴ molecules

• 8.6 x 10^-24 molecules