# Tutor profile: Michael D.

## Questions

### Subject: Physical Chemistry

Consider an ideal gas with a volume of V1. To what volume would you need to compress the gas to double its pressure? Express your answer in terms of V1.

First, recall the Ideal gas law, PV=nRT. We can use Boyle's law to answer this question, which is P1*V1=P2*V2 for an ideal gas where T and n are constant. If we want double the initial pressure (P1), we can write P2 as 2 * P1, then solve Boyle's law for V2. P1 * V1 = (2 * P1) * V2 (P1 * V1) / (2 * P1) = V2 Both P1 on the left side cancel out, leaving us with: (V1)/2 = V2

### Subject: Chemistry

What is the molarity of a NaOH solution if 25.00 mL is required to completely neutralize 40.00 mL of a 1.50 M solution of HBr.

First, calculate the amount of H+ in solution before the NaOH was added. First step of this is to find the moles of HBr in the solution. (1.50 moles HBr/1 L) * (1 L/1000 mL) * 40.00 mL=0.06 moles HBr Because HBr is a strong acid it dissociates completely, so 0.06 moles of HBr produces 0.06 moles H+ (0.06 moles HBr = 0.06 moles H+). To completely neutralize this amount we have to add 0.06 moles of OH-. NaOH is a strong acid, so similarly 0.06 moles of NaOH produces 0.06 moles of OH- (0.06 moles OH- = 0.06 moles NaOH). Then we take that and the volume added (25) to find the concentration. (0.06 moles NaOH/25 mL) * (1000 mL / 1 L) = 2.4 M NaOH.

### Subject: Basic Chemistry

Calculate the pH of the following solution: 0.01 M HCl

Because HCl is a strong acid, it dissociates completely. As a result, 0.01M HCl forms 0.01M H+ when dissolved in water. Because pH is equal to -log[H+], all we need is to solve -log[0.01]. Solving -log[0.001] with a calculator gives the pH value 4.61.