Question

How many moles are in 2.4g of carbon dioxide (CO2)?

Answer 1

Answer:

$\boxed {\boxed {\sf 0.055 \ mol \ CO_2}}$

Explanation:

To convert form grams to moles, the molar mass must be used. This is the mass (in grams) in 1 mole of a substance.

We can use the values on the Periodic Table. First, find the molar masses of the individual elements: carbon and oxygen.

• C: 12.011 g/mol
• O: 15.999 g/mol

Check for subscripts. The subscript of 2 after O means there are 2 oxygen atoms, so we have to multiply oxygen's molar mass by 2 before adding.

• O₂: 2* (15.999 g/mol)=31.998 g/mol
• CO₂: 12.011 g/mol + 31.998 g/mol =40.009 g/mol

Use the molar mass as a ratio.

$\frac {44.009 \ g\ CO_2}{ 1 \ mol \ CO_2}$

Multiply by the given number of grams.

$2.4 \ g \ CO_2 *\frac {44.009 \ g\ CO_2}{ 1 \ mol \ CO_2}$

Flip the fraction so the grams of carbon dioxide cancel.

$2.4 \ g \ CO_2 *\frac { 1 \ mol \ CO_2}{44.009 \ g\ CO_2}$

$2.4 *\frac { 1 \ mol \ CO_2}{44.009}$

$\frac { 2.4 \ mol \ CO_2}{44.009}= 0.0545342998 \ mol \ CO_2$

The original measurement of grams has 2 significant figures, so our answer must have the same. For the number we calculated, that is the thousandth place.

The ten thousandth place has a 5, so we round the 4 to a 5.

$0.055 \ mol \ CO_2$

2.4 grams of carbon dioxide is about 0.055 moles.