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Pachacha [2.7K]
2 years ago
14

4. How many moles of gold (Au) are in a pure gold nugget having a mass of 25.0 grams.

Chemistry
2 answers:
ikadub [295]2 years ago
3 0
<h3>Answer:</h3>

0.127 mol Au

<h3>General Formulas and Concepts:</h3>

<u>Math</u>

Order of Operations: BPEMDAS

  1. Brackets
  2. Parenthesis
  3. Exponents
  4. Multiplication
  5. Division
  6. Addition
  7. Subtraction
  • Left to Right

<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>

  1. [DA] Set up:                                                                                                     \displaystyle 25.0 \ g \ Au(\frac{1 \ mol \ Au}{196.97 \ g \ Au})
  2. [DA] Multiply/Divide [Cancel out units:                                                          \displaystyle 0.126923 \ mol \ Au

<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

Julli [10]2 years ago
3 0

Answer:

\boxed {\boxed {\sf 0.127 \ mol \ Au}}

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.

\frac {196.96657 \ g\ Au }{1 \ mol \ Au}

Multiply by the given number of grams.

25.0 \ g \ Au*\frac {196.96657 \ g\ Au }{1 \ mol \ Au}

Flip the fraction so the grams of gold will cancel.

25.0 \ g \ Au*\frac {1 \ mol \ Au}{196.96657 \ g\ Au }

25.0*\frac {1 \ mol \ Au}{196.96657  }

\frac {25.0 \ mol \ Au}{196.96657  }

0.1269250919 \ mol \ Au

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.

0.127 \ mol \ Au

25.0 grams of gold is about 0.127 moles of gold.

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