Module 2: Compounds and how they interact

What is the atomic number of calcium?

Mathematical Equivalence

OFF

What is the molar mass of SF₆?

You will need your periodic table to answer this question.

Mathematical Equivalence

ON

Answer explanation

Use your periodic table to find the atomic mass of sulfur and fluorine. Recall that atomic mass is the larger number that is usually written as a decimal.

What is the molar mass of H₂O₂?

You will need your periodic table to answer this question.

Mathematical Equivalence

ON

Answer explanation

Use your periodic table to find the atomic mass of hydrogen and oxygen. Recall that atomic mass is the larger number that is usually written as a decimal.

A problem asks how many grams are in 0.85 mol of NaCl.

Which option correctly sets up this problem?

The molar mass of NaCl is 58.443 g/mol

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Answer explanation

The key info you need from the problem is that you are starting with mol NaCl and want to end with grams NaCl. The problem tells you the molar mass of NaCl in g/mol, which is the one step in your path.

What you start with always goes first (0.85 mol), and then what does up must come down, so we must put mol NaCl on the bottom of the fraction. This way, the mol cancels out and we are left with units of g, which is what we wanted. Yay!

A cup of coffee contains 4.89 x 10^-4 mol of caffeine. How many molecules of caffeine is this?

• 4.89 x 10^4 molecules
• 2.94 x 10^10 molecules
• 4.89 x 10^20 molecules
• 2.94 x 10^20 molecules

Answer explanation

Match the examples to the type of chemical reaction

• Fe + Cl₂ -->
  FeCl₂

• Double replacement

• NaCl + AgNO₃ -->
  AgCl + NaNO₃

• Single replacement

• Fe₂O₃ + Al -->
  Al₂O₃ + Fe

• Decomposition

• NH₄Cl -->
  NH₃ + HCl

• Combination

Type of chemical reaction that involves the joining of two substances to form one compound

• Decomposition reaction
• Single replacement reaction

• Double replacement reaction

• Combination reaction

A + B --> AB

This is an example of what type of reaction?

• Decomposition reaction
• Single replacement reaction

• Double replacement reaction

• Combination reaction

CD + XY --> CY + XD
This is an example of what type of reaction?

• Decomposition reaction
• Single replacement reaction

• Double replacement reaction

• Combination reaction

Oxidation is ​ (a)   of electrons.

Reduction is ​ (b)   of electrons.

• loss
• gain