A gas exerts a pressure of 0.74 atm in a certain container. Suddenly, a chemical change occurs that consumes half of the molecules originally present and forms two new molecules for every three consumed. Determine the new pressure in the container if the volume of the container and the temperature are unchanged. The reaction that occurs is: 3A(g) —> 2B(g)

Explanation:

When the volume and temperature of a gas are unchanged, the pressure is directly related to the number of molecules, this is:

Or:

Thus:

For the reaction 3A(g) → 2B(g), n₁ = 3 and n₂ = 2.

Then:

As you see, the pressure decreases, because the number of molecules decreases.

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6