Today, we review Blueprint’s MCAT Diagnostic, C/P Discrete Part 2. Tune in to discover why you got it right… or wrong. We’re joined by Nicole from Blueprint MCAT. If you would like to follow along on YouTube, go to premed.tv.
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[03:36] Question 28
Which of the following properties explains why sound wave velocity increases as it travels from air to a liquid medium at the same temperature?
A.Kinetic energy of the medium
B.Volume of the medium
C.Density of the medium
D.Bulk modulus of the medium
A lot of students actually fall for answer choice C here. The density of a medium does affect the speed of propagation, however, there is an answer choice here that actually affects that speed even more, and it’s actually the bulk modulus of the medium.
Bulk modulus refers to the stiffness of a medium. So if you’re an equation person you’d like to see the math behind it. The actual equation for sound velocity is:
Your speed of sound is going to increase with your stiffness. Solids are stiffer than liquids, and liquids are more solid than gas. And so, when we’re comparing the solids and the gas, the density in that equation is going to have a smaller effect than stiffness.
There’s a larger difference in the stiffness than there is in the density. So this is definitely a tricky question that relies on not only just being able to plug and chug in that equation but having some of the conceptual understanding behind it.
Correct Answer: D
[06:19] Question 29
Modern MRI machines use electricity to generate their magnetic fields inside a circular chamber instead of using permanent magnets. Which of the following would NOT increase the strength of the MRI field?
A.Increased radius of the MRI chamber
B.Increased power supplied to the MRI machine
C.Decreased resistance of the MRI machine
D.Increased current through the MRI machine
The equation for the magnetic field generated at the center of a loop circuit is:
B=μ0I2R(at center of loop)
If you went through the rest of these answer choices, specifically increased power (answer choice B), decreased resistance (answer choice C), or increased current (answer choice D), those are all either directly saying increased current, essentially, when you look at B= IR.
Correct Answer: A
[09:34] Question 30
The two steps of the Vitamin D synthesis are summarized below.
Step 1: 7-dehydrocholesterol + UV light ⇒ previtamin D3
ΔG = -134 kJ/mol
Step 2: previtamin D3 ⇒ cholecalciferol (Vitamin D)
ΔG = +58 kJ/mol
What is the ΔG for Vitamin D synthesis?
We’re given two reactions here which are step one and step two of a larger overall reaction. We’re given the ΔG and since we’re asked about the overall ΔG, you just add them all together.
Correct Answer: B
[13:09] What to Do at the End of This Section
Nicole recommends that students sit back, take five seconds, and take two deep breaths. You just got through a whole section, it was probably a little tiring and a little difficult.
On your Navigation page, there’s a function to only review your flagged questions. And so, it will directly take you through your flagged questions.