Question

How many moles would you need to have 7.85 x 10^22 molecules of ammonia (NH3).

Answer 1

0.130 moles NH₃

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

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

Stoichiometry

• Using Dimensional Analysis

Step-by-step explanation:

Step 1: Define

[Given] 7.85 × 10²² molecules NH₃

[Solve] moles NH₃

Step 2: Identify Conversions

Avogadro's Number

Step 3: Convert

1. [DA] Set up:
   `\displaystyle 7.85 \cdot 10^(22) \ molecules \ NH_3((1 \ mol \ NH_3)/(6.022 \cdot 10^(23) \ molecules \ NH_3))`
2. [DA] Multiply/Divide [Cancel out units]:
   `\displaystyle 0.130355 \ moles \ NH_3`

Step 4: Check

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

0.130355 moles NH₃ ≈ 0.130 moles NH₃