Chemistry Quiz 3.4: Counting Atoms

How many oxygen atoms are in chemical formula 6H₂O ?

• 1

• 2

• 6

• 12

• 0

(NH₄)₂CrO₄

The above chemical formula contains:

​ (a)   nitrogen atoms;​ (b)   hydrogen atoms; ​ (c)   Chromium atoms, ​ (d)   oxygen atoms

• 5
• 3
• 2
• 8
• 1
• 4
• 10
• 6
• 32
• 7

Atomic mass is measured in ​ (a)   and molar mass is measured in ​ (b)   .

• (unified) atomic mass units
• grams per mole
• atomic units
• kilograms
• liters per mole
• different units depending on the situation

From left to right, each jar contains exactly one mole of carbon, sulfur, and aluminum, respectively. Which jar contains the most atoms?

• The jar of carbon.

  12.011 g/mol

• The jar of sulfur.

  32.066 g/mol

• The jar of aluminum.

  26.982 g/mol

• All three jars have the same number of atoms.

Note the mass of a copper(I) oxide formula unit in the image. What is the mass of 8.250 moles of Cu₂O? (Use scratch paper, a calculator and apply dimensional analysis. Label with correct unit. Sig Fig rules apply.)

(a)  

1. What is the mass of 8.12 × 10²³ molecules of CO₂ gas?

2. (Atomic mass of carbon = 12.011 u; oxygen = 15.999 u.)

3. Use scratch paper, calculator, and dimensional analysis.

4. Sig fig rules apply. Label the unit.

(a)  

1. Sulfuric acid (H₂SO₄) has a molar mass of 98.1 g/mol.

2. How many oxygen atoms are found in 75.0 g of H₂SO₄?

(Hint: Step 1 -Find the number of H₂SO₄ moles in 75.0g

Step 2- Find the number of H₂SO₄ units in that(step1) amount of moles

Step 3- find how many oxygen atoms are in that(step2) number of formula units.)

Mathematical Equivalence

ON

What is the molar mass of 1 mole of FeCl₂?

• 55.845 g/mol

• 35.453 g/mol

• 182.60 g/mol

• 126.75 g/mol

• 147.14 g/mol