Question 34 Answer and Explanation _ACT June 2009 Form 67C Science Section

34. Which of the following best explains why equal masses of O₂ and CO₂ at the same temperature and in the same-size vessel had different pressures? The pressure exerted by the O₂ was:

F. less, because there were fewer O₂ molecules per gram than there were CO₂ molecules per gram.

G. less, because there were more O₂ molecules per gram than there were CO₂ molecules per gram.

H. greater, because there were fewer O₂ molecules per gram than there were CO₂ molecules per gram.

J. greater, because there were more O₂ molecules per gram than there were CO₂ molecules per gram.

Answer and Explanation

Your Answer is

Correct Answer is J

Explanation

The formula for gas pressure in a closed container is P=nRT/V, where n is the number of molecules, R is a constant, T is the temperature, and V is the volume of the container.

The greater the number of molecules, the greater the P. CO₂ and O₂ with the same mass, O₂ has more molecules (because CO₂ The molecular mass is 44, which is larger than the 32 of O₂, so to achieve the same mass, you need more O₂ molecules), O₂ >The pressure is strong