Respuesta :

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Answer:

1.37 × 10²³ formula units MgCl₂

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

Stoichiometry

  • Using Dimensional Analysis

Explanation:

Step 1: Define

[Given] 21.6 g MgCl₂

Step 2: Identify Conversions

Avogadro's Number

[PT] Molar Mass of Mg - 24.31 g/mol

[PT] Molar Mass of Cl - 35.45 g/mol

Molar Mass of MgCl₂ - 24.31 + 2(35.45) = 95.21 g/mol

Step 3: Convert

  1. [DA] Set up:                                                                                                     [tex]\displaystyle 21.6 \ g \ MgCl_2(\frac{1 \ mol \ MgCl_2}{95.21 \ g \ MgCl_2})(\frac{6.022 \cdot 10^{23} \ formula \ units \ MgCl_2}{1 \ mol \ MgCl_2})[/tex]
  2. [DA] Multiply/Divide [Cancel out units]:                                                        [tex]\displaystyle 1.36619 \cdot 10^{23} \ formula \ units \ MgCl_2[/tex]

Step 4: Check

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

1.36619 × 10²³ formula units MgCl₂ ≈ 1.37 × 10²³ formula units MgCl₂

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