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How many moles of water were lost if the amount of water lost was 0.456 grams? Do not include units and assume three significant figures in all numbers. Be sure to include the zero before the decimal if the number is less than one.

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Answer:

0.0253 mol 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

Stoichiometry

  • Using Dimensional Analysis

Explanation:

Step 1: Define

[Given] 0.456 g H₂O (water)

Step 2: Identify Conversions

[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 0.456 \ g \ H_2O(\frac{1 \ mol \ H_2O}{18.02 \ g \ H_2O})[/tex]
  2. [DA] Multiply/Divide [Cancel out units]:                                                          [tex]\displaystyle 0.025305 \ mol \ H_2O[/tex]

Step 4: Check

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

0.025305 mol H₂O ≈ 0.0253 mol H₂O