What is the ratio of carbon to oxygen atoms in carbon dioxide (CO2)?
A2:1
B1:2
C1:1
D2:2
In CO2, there is 1 carbon atom and 2 oxygen atoms per molecule, giving a carbon-to-oxygen ratio of 1:2. This ratio holds no matter how many molecules of CO2 you have.
Question 2 True / False
Changing the subscripts in a chemical formula creates a different substance.
TTrue
FFalse
Answer: True
Subscripts define which compound a formula represents. H2O (water) has 2 hydrogen atoms per oxygen atom. H2O2 (hydrogen peroxide) has 2 hydrogen atoms and 2 oxygen atoms — a different ratio and a completely different substance with different properties. Altering subscripts means altering the compound.
Question 3 Short Answer
A molecule has the formula C2H6. How many total atoms are in one molecule, and what is the ratio of carbon to hydrogen?
Think about your answer, then reveal below.
Model answer: 8 total atoms (2 carbon + 6 hydrogen), with a carbon-to-hydrogen ratio of 2:6, which simplifies to 1:3.
The subscript after C is 2 (2 carbon atoms) and after H is 6 (6 hydrogen atoms), giving 8 atoms total. The ratio 2:6 reduces to 1:3, meaning for every carbon atom there are three hydrogen atoms. This compound is ethane.