Question

Given the equation 2Si(s) + 2Cl2(g) --> 2SiCl2(g) + 687 kJ, how much heat is produced when 106 g of Cl2 react?

Answer 1

514 kJ

General Formulas and Concepts:

Atomic Structure

• Reading a Periodic Table
• Elements
• Compounds
• Moles

Stoichiometry

• Analyzing Reactions rxn
• Using Dimensional Analysis

Step-by-step explanation:

Step 1: Define

Identify

[Given] rxn (balanced): 2Si (s) + 2Cl₂ → 2SiCl₂ (g) + 687 kJ

[Given] 106 g Cl₂

[Solve] kJ heat

Step 2: Identify Conversions

[rxn] 2 mol Cl₂ → 687 kJ

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

Molar Mass of Cl₂: 2(35.45) = 70.9 g/mol

Step 3: Stoichiometry

1. [DA] Set up:
   `\displaystyle 106 \ g \ Cl_2((1 \ mol \ Cl_2)/(70.9 \ g \ Cl_2))((687 \ kJ)/(2 \ mol \ Cl_2))`
2. [DA] Divide/Multiply [Cancel out units]:
   `\displaystyle 513.554 \ kJ`

Step 4: Check

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

513.554 kJ ≈ 514 kJ

Topic: AP Chemistry

Unit: Thermochemistry