PSAT Math Multiple-Choice Question 212: Answer and Explanation

Question: 212

In chemistry, the combined gas law formula gives the relationship between the volumes, temperatures, and pressures for two fixed amounts of gas. Which of the following gives p₂ in terms of the other variables?

• A.
• B.
• C.
• D.

Correct Answer: C

Explanation:

C

Difficulty: Easy

Category: Passport to Advanced Math/Rational Equations

Getting to the Answer: Focus on the question at the very end—it's just asking you to solve the equation for p₂. Multiply both sides by T₂ to get rid of the denominator on the right-hand side of the equation. Then divide by V₂ to isolate p₂:

Stop here! You cannot cancel the V s and T s because the subscripts indicate that they are not the same variable. In math, subscripts do not behave the same way superscripts (exponents) do. Choice (C) is correct.