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How many grams are in 3.14 moles of PI₃?

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Answer:


\boxed {\boxed {\sf 1290 \ g \ PI_3}}

Step-by-step explanation:

We want to convert from moles to grams, so we must use the molar mass.

1. Molar Mass

The molar mass is the mass of 1 mole of a substance. It is the same as the atomic masses on the Periodic Table, but the units are grams per mole (g/mol) instead of atomic mass units (amu).

We are given the compound PI₃ or phosphorus triiodide. Look up the molar masses of the individual elements.

  • Phosphorus (P): 30.973762 g/mol
  • Iodine (I): 126.9045 g/mol

Note that there is a subscript of 3 after the I in the formula. This means there are 3 moles of iodine in 1 mole of the compound PI₃. We should multiply iodine's molar mass by 3, then add phosphorus's molar mass.

  • I₃: 126.9045 * 3=380.7135 g/mol
  • PI₃: 30.973762 + 380.7135 = 411.687262 g/mol

2. Convert Moles to Grams

Use the molar mass as a ratio.


\frac {411.687262 \ g \ PI_3}{ 1 \ mol \ PI_3}

We want to convert 3.14 moles to grams, so we multiply by that value.


3.14 \ mol \ PI_3 *\frac {411.687262 \ g \ PI_3}{ 1 \ mol \ PI_3}

The units of moles of PI₃ cancel.


3.14 *\frac {411.687262 \ g \ PI_3}{ 1 }


1292.698 \ g\ PI_3

3. Round

The original measurement of moles has 3 significant figures, so our answer must have the same. For the number we calculated, that is the tens place.

  • 1292.698

The 2 in the ones place tells us to leave the 9.


1290 \ g \ PI_3

3.14 moles of phosphorous triiodide is approximately equal to 1290 grams of phosphorus triodide.

User Bamdad
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