Next, we have the simplest members of the quinone class. Let’s quickly draw those:įirst we have 1,4-benzenediol is also known as hydroquinone and has two hydroxyl groups attached to opposite ends of the benzene ring at carbons C1 and C4. Quick glance at our answer choices, we know we’re dealing with either hydroquinone or benzoquinione as our starting substances. We have our structure here, and we’re expected to know how it is formed. That means we’ll need to go back to the passage and see our molecule, and we’ll likely have to know some properties about the molecule. That means D matches our breakdown and is our best answer.Ģ) DHB was the coating on our plate in the passage, so we want to know the reaction that leads to its formation. We only dealt with whole number answers and we didn’t round during our calculation. 9 kV/m Units are good, our numeric value matches our predicted value exactly, and there’s no room for rounding errors here.A lot of times the test maker will make that a potential answer choice, because they know students will make that mistake. Another observation I want to make: Even if we combined our numbers incorrectly and divided 0.5 meters by 4.5 kilovolts by accident here, we still haven’t stumbled across a potential answer. 6 kV/m once again, closer, but not 9 kilovolts per meter.
When you get into larger numbers or more complex equations, that can change. Remember with math problems, and especially when we don’t round or estimate any numbers, you’ll often find the exact answer you solved for.
Looking at the 4 options, every answer choice is in units where only voltage and travel distance can combine to give us a correct answer. In fact, we thought we’d have to use the exact numbers we did to solve the problem before even thinking about any specifics. Now that’s convenient isn’t it?! We knew coming in, our answer choices were going to have these units. Divide these two numbers and we have 9.0 kilovolts/meters. We’re given a voltage of 4.5 kV, and also told a travel distance of 0.5 m. Said differently, the magnitude of the electric field is equal to voltage divided by distance. The voltage across plates is given by the magnitude of our electric field times the distance between the plates. So, we’ve essentially isolated the source of our answer to a few options, before even having to dive into solving for the magnitude of the electric field.īut now, we have to think to our physics content and how we can answer this question. Travel distance is given as 0.5 meters, and previously we saw wavelength was given in nanometers. Do we see any units here that correspond to kilovolts or meters? We have the 4.5 kilovolt electric voltage between the MALDI plate and MS detector.
We’re back at our passage here, and before we go into specific details, remember the units we saw in the answer choices: kilovolts over meters. Also, this is a math problem that is asking for a quantitative value, magnitude, so make a mental note of the units of the answer choices. When you’re actually practicing or taking the exam, going back to the passage (unless it’s for specific details you don’t want to memorize) can be a waste of time. All I’m doing is walking you through the important parts here, just to be thorough. I want you to keep in mind when you go back to the passage like this, I don’t want you re-reading the entire passage or even entire paragraphs. The question stem itself mentions this question is at least partially passage-based so we can reference the necessary part of the passage. Section Bank: Chemical and Physical Foundations of Biological Systems: Passage 1ġ) This question references the uniform electric field described in the passage and we’re asked its magnitude specifically.
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