Question

How many moles of carbon dioxide (CO2) are produced from 15.6 grams of baking soda (NaHCO3)

Answer 1

Step 1 - Understanding the reaction

Baking soda, NaHCO3, can be heated untill it decomposes. The decomposition reaction is:

`2\text{NaHCO}_(3(s))\to Na_2CO_(3(s))+H_2O_((l))+CO_(2(g))`

Note that 2 moles of NaHCO3 produce 1 mole of CO2.

Step 2 - Using the reaction to solve the problem

Now we can convert this relation in moles to a relation in grams. We just have to multiply each number of moles by the respective molar mass of the substance (for NaHCO3, 84 g/mol; for CO2, 44 g/mol):

`m_{\text{NaHCO}3}=2*84=168\text{ g of NaHCO3}`

Since we want to discover how many moles of CO2 are formed, and not how many grams, we don't need to multiply its number of moles by its molar mass.

Let's note then that:

2 moles of NaHCO3 produce 1 mole of CO2

2 moles of NaHCO3 corresponds to 168 g of NaHCO3

Therefore:

168 g of NaHCO3 produce 1 mole of CO2

This is a fixed proportion and we'll use it to solve the exercise. Since we want to know how many moles of CO2 are formed from 15.6 g of NaHCO3, we can set the following proportion:

`\begin{gathered} 168\text{ g of NaHCO3 produce ---- 1 mole of CO2} \\ 15.6\text{ g of NaHCO3 produce ---- x} \\ \\ x=(15.6)/(168)=9.3*10^(-2)\text{ moles of CO2} \end{gathered}`

9.3*10(-2) moles of CO2 would be produced thus from 15.6 grams of baking soda.