Question

How many atoms are in 0.500 g of Magnesium Chloride?

Answer 1

3.16 × 10²¹ atoms MgCl₂

General Formulas and Concepts:

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

• Molar Mass - how many grams of an element/compound in 1 mol of that substance

• Reading a Periodic Table of Elements

Step-by-step explanation:

Step 1: Define

0.500 g MgCl₂ (Magnesium Chloride)

• Mg has a 2+ charge
• Cl has a 1- charge
• Need to balance the charges

Step 2: Define conversion

Molar Mass of Mg - 24.31 g/mol

Molar Mass of Cl - 35.45 g/mol

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

Avagadro's Number: atoms

Step 3: Dimensional Analysis

`0.500 \ g \ MgCl_2((1 \ mol \ MgCl_2)/(95.21 \ g \ MgCl_2) )((6.022 \cdot 10^(23) \ atoms \ MgCl_2)/(1 \ mol \ MgCl_2) )` = 3.16248 × 10²¹ atoms MgCl₂

Step 4: Check

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

3.16248 × 10²¹ atoms MgCl₂ ≈ 3.16 × 10²¹ atoms MgCl₂