When methane is burned with oxygen,the products are carbon dioxide and water.If you produce 18 grams of water from 8 grams of methane and 32 grams of oxygen,how many grams of carbon dioxide were produced in the reaction?

Question

Quizplus · Accepted Answer

First, we need to balance the chemical equation for the reaction: 
CH4 + 2O2 → CO2 + 2H2O 
From the balanced equation, we can see that for every 1 mole of methane that reacts, 1 mole of carbon dioxide is produced. 
To find out how many moles of methane reacted, we need to convert the given mass to moles: 
8g CH4 / 16.04 g/mol = 0.499 moles CH4 
To find out how many moles of oxygen reacted, we also need to convert the given mass to moles: 
32g O2 / 32 g/mol = 1 mole O2 
Since oxygen reacts with methane in a 2:1 ratio, we can see that there is excess oxygen left over after the reaction. To find out how much excess oxygen, we need to subtract the amount of oxygen that reacted from the amount that was given: 
1 mole O2 - 0.5 moles CH4 = 0.5 moles O2 
Now we can use the amount of water produced to find out how many moles of oxygen reacted: 
18g H2O / 18.02 g/mol = 0.999 moles H2O 
Since each mole of water produced requires 2 moles of oxygen, we can find out how many moles of oxygen reacted by dividing the moles of water produced by 2: 
0.999 moles H2O / 2 = 0.4995 moles O2 
We can see that this is very close to the amount of oxygen that reacted with methane, so we can assume that all of the methane reacted completely. 
Therefore, we produced 0.499 moles of carbon dioxide. To find out how much this is in grams, we can use the molar mass of carbon dioxide: 
0.499 moles CO2 x 44.01 g/mol = 21.9 g CO2 
This is closest to answer choice B, 22 grams.

When Methane Is Burned with Oxygen,the Products Are Carbon Dioxide