4. How many moles of gold (Au) are in a pure gold nugget having a mass of 25.0 grams.
2 answers:
<h3>
Answer: </h3>
0.127 mol Au
<h3>
General Formulas and Concepts: </h3>
<u>Math</u>
Order of Operations: BPEMDAS
Brackets Parenthesis Exponents Multiplication Division Addition Subtraction <u>Chemistry</u>
<u>Atomic Structure</u>
Reading a Periodic Table Moles <u>Stoichiometry</u>
Using Dimensional Analysis <h3>
Explanation: </h3>
<u>Step 1: Define</u>
[Given] 25.0 g Au
[Solve] moles Au
<u>Step 2: Identify Conversions</u>
[PT] Molar Mass of Au - 196.97 g/mol
<u>Step 3: Convert</u>
[DA] Set up: [DA] Multiply/Divide [Cancel out units:
<u>Step 4: Check</u>
<em>Follow sig fig rules and round. We are given 3 sig figs.</em>
0.126923 mol Au ≈ 0.127 mol Au
Answer:
Explanation:
To convert from mass to moles, the molar mass must be used. This can be found on the Periodic Table.
Gold (Au): 196.96657 g/mol Use this number as a ratio.
Multiply by the given number of grams.
Flip the fraction so the grams of gold will cancel.
The original measurement has 3 significant figures, so the answer must have the same. For the number we calculated that is the thousandth place. The 9 in the ten thousandth place tells us to round the 6 to a 7.
25.0 grams of gold is about 0.127 moles of gold.
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