Question

How many moles is 287.7 grams of Iridium (Ir)?

Answer 1

`\boxed {\boxed {\sf About \ 1.497 \ mol \ Ir }}`

Step-by-step explanation:

To convert from grams to moles, we must the molar mass of iridium, which can be found on the Periodic Table.

• Ir: 192.22 g/mol

Use the molar mass as a ratio.

`( 192.22 \ g \ Ir)/( 1 \ mol \ Ir)`

Multiply by the given number of grams: 287.7

`287.7 \ g Ir *( 192.22 \ g \ Ir)/( 1 \ mol \ Ir)`

Flip the fraction so the grams of Iridium will cancel.

`287.7 \ g Ir *(1 \ mol \ Ir )/( 192.22 \ g \ Ir)`

`287.7 *(1 \ mol \ Ir )/( 192.22 )`

`\frac {287.7 \ mol \ Ir }{192.22} \\`

Divide.

`1.49672251 \ mol \ Ir`

The original measurement has 4 significant figures, so we must round our answer to 4 sig figs as well. For the answer we calculated, that is the thousandth place.

The 7 in the ten thousandth place tells us to round the 6 up to a 7.

`1.497 \ mol \ Ir`

There are about 1.497 moles of iridium in 287.7 grams.

Answer 2

1.497 mol Ir

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

Stoichiometry

• Using Dimensional Analysis

Step-by-step explanation:

Step 1: Define

287.7 g Ir

Step 2: Identify Conversions

[PT] Molar Mass of Ir - 192.22 g/mol

Step 3: Convert

1. Set up:
   `\displaystyle 287.7 \ g \ Ir((1 \ mol \ Ir)/(192.22 \ g \ Ir))`
2. Multiply/Divide:
   `\displaystyle 1.49672 \ mol \ Ir`

Step 4: Check

Follow sig fig rules and round. We are given 4 sig figs.

1.49672 mol Ir ≈ 1.497 mol Ir