The APsolute RecAP: Chemistry Edition

Melanie Kingett, Sarah Rayder, Brad Kingett, Zach Caruso

The APsolute RecAP: Chemistry Edition, written by Sarah Rayder and hosted by Melanie Kingett, will be your guide to scoring the five! The APsolute RecAP is designed to maximize your understanding and minimize your need for memorization. Each episode will review content, skills and test taking tips to help you succeed in May. (AP is a registered trademark of the College Board and is not affiliated with The APsolute RecAP. Copyright 2020 - The APsolute RecAP, LLC. All rights reserved.) read less
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Episodes

The APsolute RecAP: Chemistry Edition - Episode 59: Unit 6 selected FRQs
Dec 20 2021
The APsolute RecAP: Chemistry Edition - Episode 59: Unit 6 selected FRQs
Unit 6 is all about the big idea Energy (0:46). Episode 59 discusses the questions 2021 - Question 4, 2017 - Question 5 and 2013 - Question 3. These are released FRQs from previous exams and copyright of the College Board.Question 4 of the 2021 exam starts with our favorite equation: mcAT (1:34). In part b) you calculate the mass of iron and in part (c) discuss the effect of doubling the mass of iron on the maximum temperature. Question 5 of the 2017 looks at similar concepts, but it is a combustion reaction (3:40). It starts again with calculating the magnitude of heat energy and using mcAT. In part (b) we calculate how much energy 1 mole of 2-propanol would release. Part (c) asks about the effect of having a water/propanol mixture on the final temperature. Question 3 of the 2013 exam starts with stoichiometry - identifying the limiting reactant (5:30) and in part (b) the inconsistent trial. In (c) we are using again mCAT for our calculations. (D) and (e) have us calculate the enthalpy - in d) using experimental data, in (e) as enthalpy of formation. In (f) we are provided with an explanation for the discrepancy between (d) and (e) and are asked to explain if that could be the reason.Today’s Question of the day is about Enthalpy. How do we calculate the enthalpy using bond enthalpies?A. bonds broken - bonds formed B. bonds formed - bonds broken C. bonds broken + bonds formed D. bonds formed + bonds brokenThank you for listening to The APsolute RecAP: Chemistry Edition!(AP is a registered trademark of the College Board and is not affiliated with The APsolute RecAP. Copyright 2021 - The APsolute RecAP, LLC. All rights reserved.)Website:www.theapsoluterecap.comEMAIL:TheAPsoluteRecAP@gmail.comFollow Us:INSTAGRAMTWITTERFACEBOOKYOUTUBE
The APsolute RecAP: Chemistry Edition - Episode 56: Concentration Changes Over Time
Nov 22 2021
The APsolute RecAP: Chemistry Edition - Episode 56: Concentration Changes Over Time
An AP Chemistry classic experiment for concentration changes over time is determining the rate law of fading Crystal Violet. (1:07) If the reaction is zero order, the plot of our concentration of our reactant vs time is linear. (2:51) If the reaction is first order with respect to our crystal violet, a plot of the natural log of the concentration of the reactant vs time will be linear. (3:17) If the reaction is second order with respect to crystal violet, a plot of 1 over concentration vs time will be linear. (3:45) We can use the graph and determine k as follows: for zeroth and first order k equals - slope and for second order reactions k = slope. (5:03) Integrated rate laws can be used to calculate the concentration after a specific amount of time or to determine how long a reaction has to run to get a specific concentration. A specific application of the rate laws is half-life. In AP Chemistry, half-life is always a first-order reaction. (6:15)Question: If you have a reaction with a half-life of 4 days and an initial concentration of 0.1M, what fraction will be left after 20 days? (8:30)Thank you for listening to The APsolute RecAP: Chemistry Edition!(AP is a registered trademark of the College Board and is not affiliated with The APsolute RecAP. Copyright 2021 - The APsolute RecAP, LLC. All rights reserved.)Website:www.theapsoluterecap.comEMAIL:TheAPsoluteRecAP@gmail.comFollow Us:INSTAGRAMTWITTERFACEBOOKYOUTUBE
The APsolute RecAP: Chemistry Edition - Episode 55: Unit 4 Selected FRQs
Nov 15 2021
The APsolute RecAP: Chemistry Edition - Episode 55: Unit 4 Selected FRQs
Unit for is a mix of foundational skills, like stoichiometry, and an introduction to later topics (0:32). The questions in this episode are: 2018 - Question 3 d) through i) and 2014 - Question 1 a) - f).These are released FRQs from previous exams and copyright of the College Board (1:32). 2018 starts with three questions from a different unit. Part d) asks for a redox reaction (2:05). In part e) you are asked to calculate the concentration of iron(ii)plus in the solution (2:36) and in f) to discuss lab equipment (3:58). G) and i) refer to a second experiment involving iron impurities (4:39) and the effect of incomplete oxidation (5:34). Question 1 from 2014 is a gravimetric analysis with the goal of determining the iodide content in a potassium iodide tablet (7:00). Therefore we write the net-ionic equation (7:22), reflect on our data (7:52) and ion concentrations (8:06) before we calculate the number of moles of precipitate (8:23) and percentage iodide (8:53). Part f) concludes with a question about a potential error (9:38).Question: True or false: You MUST indicate the state of matter in parentheses in your balanced chemical equation, even if not asked for it.Thank you for listening to The APsolute RecAP: Chemistry Edition!(AP is a registered trademark of the College Board and is not affiliated with The APsolute RecAP. Copyright 2021 - The APsolute RecAP, LLC. All rights reserved.)Website:www.theapsoluterecap.comEMAIL:TheAPsoluteRecAP@gmail.comFollow Us:INSTAGRAMTWITTERFACEBOOKYOUTUBE
The APsolute RecAP: Chemistry Edition - Episode 54: Unit 3 Selected FRQs
Nov 8 2021
The APsolute RecAP: Chemistry Edition - Episode 54: Unit 3 Selected FRQs
The FRQs discussed in this episode are the question 4s from the 2019, 2018 and 2017 AP Exam. These are released FRQs from previous exams and copyright of the College Board (0:23).Question 4 of the 2018 exam focuses on comparing the IMFs of CS2 and COS, asking you to explain why CS2 has a higher boiling point (1:48). The second part has you calculate the pressure of CS2 using the ideal gas law (3:11). In question 4 of the 2019 exam you describe the effect of raising the temperature on the motion of the CO2 particles connecting temperature and particle speed (4:09). In part b you calculate the new pressure under constant volume (4:59), in part c) you describe why the pressure increases (6:35) and in part d you compare an ideal and a real gas (7:19). Question 4 of the 2017 exam focuses in Chromatography, identifying the least polar dye by discussing the interactions between dye and solvent/paper (8:29) as well as identifying an unknown by comparing how far the dye travelled (9:05).Today’s Question of the day is about FRQ Questions.True or false: The term “van-der-Waals” forces can be used instead of London Dispersion Forces.Thank you for listening to The APsolute RecAP: Chemistry Edition!(AP is a registered trademark of the College Board and is not affiliated with The APsolute RecAP. Copyright 2021 - The APsolute RecAP, LLC. All rights reserved.)Website:www.theapsoluterecap.comEMAIL:TheAPsoluteRecAP@gmail.comFollow Us:INSTAGRAMTWITTERFACEBOOKYOUTUBE
The APsolute RecAP: Chemistry Edition - Episode 53: Beer-Lambert Law
Nov 1 2021
The APsolute RecAP: Chemistry Edition - Episode 53: Beer-Lambert Law
Coffee needs to be “just right” and we can tell how strong it is by the color (0:30). We can use the color to determine concentration also in Chemistry (1:09). The color we see is determined by the wavelength an object reflects, while absorbing all other colors (1:23).The Beer-Lambert Law absorbance to molar absorptivity, path length and concentration (2:08). In AP Chemistry, the molar absorptivity and path length are held constant, therefore absorbance is directly proportional to concentration (2:28).Experimentally, we measure absorbance using spectrophotometers (4:41). To determine the concentration of, for example, blue dye in a sports drink, we have to create a calibration curve using solutions with known concentration and measuring the absorbance (5:35). We can then use the graph and a measurement of absorbance of the sports drink to determine the concentration (6:16).In which of the following examples could you use spectroscopy and the Beer-Lambert law to determine the concentration?A. Determination of bilirubin in blood plasma samples. B. Determination of colorless zinc(II) nitrate in a sample. C. Determination of ethanol (drinking alcohol) in an alcoholic beverage. D. Determination of isopropyl in hand sanitizer.Thank you for listening to The APsolute RecAP: Chemistry Edition!(AP is a registered trademark of the College Board and is not affiliated with The APsolute RecAP. Copyright 2021 - The APsolute RecAP, LLC. All rights reserved.)Website:www.theapsoluterecap.comEMAIL:TheAPsoluteRecAP@gmail.comFollow Us:INSTAGRAMTWITTERFACEBOOKYOUTUBE
The APsolute RecAP: Chemistry Edition - Listener’s Choice III
Apr 12 2021
The APsolute RecAP: Chemistry Edition - Listener’s Choice III
Our listener’s choice recaps three topics: (R)ICE tables, titrations and buffers. We start with the RICE table - what does it actually stand for? (0:49). RICE tables are best explained with an example. In our case: The reaction of gaseous hydrogen with gaseous chlorine to form gaseous hydrogen chloride - a reaction that has a K = 49. And we are calculating the concentrations at equilibrium (1:44)! Two important tips for RICE tables: (1) practice, practice, practice; (2) make assumptions (4:09).Our next two topics are connected: titrations and buffers. We start with the titration of a strong acid/strong base and discuss the calculation of the pH at several points along the titration curve (6:01). Our second example is the titration of a weak acid with a strong base. Again, we discuss the pH calculations along the titration curve, but then focus on buffers, which are formed when the weak acid is partially neutralized (7:29). The episode defines buffers and describes how they work (8:00). Moving along the titration curve, we discuss the calculations for buffers and the midway point of the titration (9:18), the calculations at equivalence point (10:03) and beyond the equivalence point.Question: What will be the approximate pH of an equimolar solution of NH3 and HCl?Thank you for listening to The APsolute RecAP: Chemistry Edition!(AP is a registered trademark of the College Board and is not affiliated with The APsolute RecAP. Copyright 2021 - The APsolute RecAP, LLC. All rights reserved.)Website:www.theapsoluterecap.comEMAIL:TheAPsoluteRecAP@gmail.comFollow Us:INSTAGRAMTWITTERFACEBOOKYOUTUBE