Answer:
1.66 × 10²⁴ atoms Al
General Formulas and Concepts:
Math
Pre-Algebra
Order of Operations: BPEMDAS 
- Brackets 
 - Parenthesis 
 - Exponents 
 - Multiplication 
 - Division 
 - Addition 
 - Subtraction 
 
Chemistry
Atomic Structure
- Reading a Periodic Table
 - Moles
 - Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.
 
Stoichiometry
- Using Dimensional Analysis
 
Step-by-step explanation:
Step 1: Define
[Given] 2.75 mol Al
[Solve] atoms Al
Step 2: Identify Conversions
Avogadro's Number
Step 3: Convert
- [DA] Set up: 

 - [DA] Multiply [Cancel out units]: 

 
Step 4: Check
Follow sig fig rules and round. We are given 3 sig figs.
1.65605 × 10²⁴ atoms Al ≈ 1.66 × 10²⁴ atoms Al