39. Let's calculate the volume of carbon dioxide.

According to Avogadro's law, the following rule applies: in equal volumes of different gases taken at the same temperatures and pressures, the same number of molecules is contained.

From the chemical reaction equation, it follows that the ratio of the amount of substance (in moles) is $2: 1$, which means the volume of carbon dioxide is half the volume of oxygen.

$V\left(\mathrm{CO}_{2}\right)=\frac{1}{2} V\left(\mathrm{O}_{2}\right)=\frac{1}{2} \cdot 14=7$ liters

Determining the volume of carbon dioxide - 4 points
Answer: 7 l.

## TOTAL 10 points

## TASK № 2

Chromium (III) oxide was melted with potassium sulfite. The resulting product was added to water. To the precipitate formed, a mixture of bromine and sodium hydroxide was added, resulting in a yellow solution. Upon adding hydrogen sulfide water to the obtained solution, a precipitate formed. Write the equations for the four described reactions.

## Solution: