Question

If you have 312 grams of calcium chloride, how many atoms would you have?

Answer 1

Answer:

1.69 × 10²⁴ atoms CaCl₂

General Formulas and Concepts:

Math

Pre-Algebra

Order of Operations: BPEMDAS

1. Brackets
2. Parenthesis
3. Exponents
4. Multiplication
5. Division
6. Addition
7. Subtraction

• Left to Right

Chemistry

Atomic Structure

• Reading a Periodic Table
• Writing Compounds
• Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

Stoichiometry

• Use Dimensional Analysis

Explanation:

Step 1: Define

312 g CaCl₂ (calcium chloride)

Step 2: Identify Conversions

Avogadro's Number

Molar Mass of Ca - 40.08 g/mol

Molar Mass of Cl - 35.45 g/mol

Molar Mass of CaCl₂ - 40.08 + 2(35.45) = 110.98 g/mol

Step 3: Convert

1. Set up:                                $\displaystyle 312 \ g \ CaCl_2(\frac{1 \ mol \ CaCl_2}{110.98 \ g \ CaCl_2})(\frac{6.022 \cdot 10^{23} \ atoms \ CaCl_2}{1 \ mol \ CaCl_2})$
2. Divide/Multiply:                                                                                               $\displaystyle 1.69298 \cdot 10^{24} \ atoms \ CaCl_2$

Step 4: Check

Follow sig fig rules and round. We are given 3 sig figs.

1.69298 × 10²⁴ atoms CaCl₂ ≈ 1.69 × 10²⁴ atoms CaCl₂