Question

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

Answer 1

Answer:

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

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:                                 $\displaystyle 287.7 \ g \ Ir(\frac{1 \ mol \ Ir}{192.22 \ g \ Ir})$
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

Answer 2

Answer:

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

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.

$\frac{ 192.22 \ g \ Ir}{ 1 \ mol \ Ir}$

Multiply by the given number of grams: 287.7

$287.7 \ g Ir *\frac{ 192.22 \ g \ Ir}{ 1 \ mol \ Ir}$

Flip the fraction so the grams of Iridium will cancel.

$287.7 \ g Ir *\frac{1 \ mol \ Ir }{ 192.22 \ g \ Ir}$

$287.7 *\frac{1 \ mol \ Ir }{ 192.22 }$

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

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.