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mezya [45]
3 years ago
14

How many moles of Si are in 78.0 grams of silicon

Chemistry
2 answers:
Igoryamba3 years ago
8 0

Answer:

\boxed {\boxed {\sf 2.78 \ mol \ Si}}}

Explanation:

To convert from grams to moles, we must use the molar mass. This number can be found on the Periodic Table.

  • Si (Silicon): 28.085 g/mol

We can use number as a ratio.

\frac { 28.085 \ g \ Si}{ 1  \ mol \ Si}

Multiply by the given number of grams.

78.0 \ g \ Si *\frac { 28.085 \ g \ Si}{ 1  \ mol \ Si}

Flip the fraction so the grams of silicon cancel.

78.0 \ g \ Si *\frac {1  \ mol \ Si }{ 28.085 \ g \ Si}

78.0  *\frac {1  \ mol \ Si }{ 28.085 }

\frac {78.0  \ mol \ Si }{ 28.085 }= 2.77728324729 \ mol \ Si

The original number of grams (78.0) has 3 significant figures, so our answer must have the same. For the number of moles calculated, that is the hundredth place. The 7 in the thousandth place tells us to round the 7 to a 8.

2.78 \ mol \ Si

There are about 2.78 moles of silicon in 78.0 grams.

gladu [14]3 years ago
6 0
The answer is 2.78 moles of Si

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