Respuesta :

Space

Answer:

2.55 × 10²⁴ molecules H₂O

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
  • Moles
  • Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

Stoichiometry

  • Using Dimensional Analysis

Explanation:

Step 1: Define

[Given] 76.4 g H₂O

[Solve] molecules H₂O

Step 2: Identify Conversions

Avogadro's Number

[PT] Molar Mass of H - 1.01 g/mol

[PT] Molar Mass of O - 16.00 g/mol

Molar Mass of H₂O - 2(1.01) + 16.00 = 18.02 g/mol

Step 3: Convert

  1. [DA] Set up:                                                                                                      [tex]\displaystyle 76.4 \ g \ H_2O(\frac{1 \ mol \ H_2O}{18.02 \ g \ H_2O})(\frac{6.022 \cdot 10^{23} \ molecules \ H_2O}{1 \ mol \ H_2O})[/tex]
  2. [DA] Divide/Multiply [Cancel out units]:                                                           [tex]\displaystyle 2.55317 \cdot 10^{24} \ molecules \ H_2O[/tex]

Step 4: Check

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

2.55317 × 10²⁴ molecules H₂O ≈ 2.55 × 10²⁴ molecules H₂O

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