chemistry
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A notoriously strange and elusive concept in chemistry: the molecular orbital. Its seemingly arbitrary patterns and applications appear in every chemistry course, yet it confuses almost every student. Here’s a step-by-step on how to draw a basic molecular orbital diagram and what it can tell you about the properties of the chemical bond between ...
For many years in academia, I have been teaching courses in what I consider the "Holy Grail of Chemistry" - Physical Chemistry (which is composed of Quantum Chemistry, Statistical Thermodynamics, Kinetics, and Chemical Dynamics. In these courses, physics, mathematics, biology, and chemistry blend together in an exquisite way to provide a ...
Intermolecular forces (IMFs) are “electrostatic” interactions between molecules – a result of all the charges floating around and interacting in the system. IMFs influence the properties of substances that we can observe and interact with – for example, the phase of the substance or its boiling point.
If we had to pick one go-to answer to explain as many things as possible in biochemistry, it would probably be “the hydrophobic effect.” It’s responsible for protein structure and function, cell membrane organization, and the distribution of drugs and metabolites. It’s often an important consideration in drug design. But what is it, and how does ...
While you might not think about it very often, gases are everywhere around us, from the air you breathe to the natural gas you might use to heat your home. To use gases safely and effectively, chemists use the ideal gas law to understand how much gas is in containers and pipes.
Ask almost any premedical student about chemistry, and you’ll get the same set of reactions. If they haven’t finished the chemistry prerequisites, it's a gulp and a look of fear. For those who have completed chemistry and are still premed, it's a sigh of relief: the hardest part is over! And for those who are currently struggling in chemistry ...
I have greeted over 1,000 students to my classroom throughout the 20+ years of teaching AP Chemistry, and the number one question I hear is “Why is chemistry so hard?” I have several responses to that question that I have offered to my students. But first, I want you to read each bullet below and notice which one resonates with you:
Maybe you were studying for the MCAT or just in your college chemistry lab when it dawned on you: why are there so many different types of chromatography? What do they have in common and what are their differences?
In this blog post, we will review how to determine the empirical formula of a compound using the mass percentages of the elements from which it is formed.
In this blog post, we explore the four quantum numbers, which allow us to describe the properties of each electron within an atom. According to the Pauli Exclusion Principle, no two electrons can share the same combination of quantum numbers. A carbon atom has six electrons, for example, and each of these electrons can be described by one of six ...
Today we will discuss VSEPR (pronounced “vesper”), which stands for valence-shell electron-pair repulsion. The basis of VSEPR is that the electrons in bonds and lone pairs repel each other. To minimize the instability that results from these repulsions, a molecule will adopt the shape that places electron groups as far apart as possible. VSEPR ...
Organic chemistry is historically considered a “weed-out” class for pre-medical students and often the cause of much frustration for students. After spending 3 years during college serving as a teaching assistant and tutor for organic chemistry courses at my undergraduate university, here are some tips for studying for your organic chemistry ...
In this blog post, we will complete the following example problem:
Balancing redox reactions is an essential skill for the Chemical and Physical Foundations section of the MCAT, the GRE Chemistry Subject Test, and the AP Chemistry Exam. Today, we will learn how to use the half-cell method for balancing redox reactions in acidic and basic solutions. We will first balance a redox reaction in acidic solution, then ...
Although there are lots of tricks that people use to write chemical formulas for ionic compounds, the best way to do it is to really understand what’s going on – that way, you’ll never use a shortcut that doesn’t work.
Dimensional analysis is the best way to do math in chemistry. With dimensional analysis, you don’t need to memorize formulas, and you can easily check your work for every problem. Because this skill is so important, it’s crucial to have a step-by-step method that you follow every time you do it.
When you've learned about pKa, you've most likely used it in acid-base calculations. However, some exams may ask you to apply a conceptual knowledge of pKa to predict whether a chemical compound is charged or uncharged.
Stoichiometry: it’s the bane of many chemistry students’ studies. It’s so easy to get tangled up in a jumble of numbers without any idea of what’s actually going on.
What is the ribosome? I find the parts of the cell are easier to keep straight if you get to know each one of them a little better. Don’t be scared; they’re your friends! Let’s talk about the ribosome.
Imagine: you’ve made it through your first semester or two of undergrad and weathered all the storms that come with this transition. And, now you find yourself facing a dreaded academic giant that has stricken fear in the hearts of scores of pre-medical students. A chemistry course unlike any other. If you are anything like most pre-medical ...
The word “chemistry” inspires so many emotions. To some, it brings about the excitement of mixing together glowing liquids and crafting the perfect radioactive potion that, when consumed, will turn you into the Incredible Hulk. To others, it’s discombobulated numbers and letters on a piece a paper in a classroom, a concatenation that strikes fear ...
Chemical engineering is a comprehensive and vast field of study with far-reaching impact. I have been a practicing chemical engineer in the biotechnology industry for the last 5 years, and prior to that, I earned my doctorate in chemical engineering at the University of Wisconsin, Madison. Over the last 10 years, I have seen the evolution and ...
Thanksgiving dinner conversations can be uncomfortable… but solution composition problems don’t have to be! Recall that a solution is a homogenous mixture of two or more substances. Chemists have come up with many ways to describe the composition of a solution. Some ways are more appropriate than others depending on the situation.
An everyday limiting reactant problem You’re expecting company and totally forgot to go grocery shopping. What on earth will you feed your guests? Sandwiches! You have some ingredients to whip up some sandwiches. So, let’s assume you are going to go through with making these sandwiches. You need 2 slices of bread, 3 slices of meat (can’t be ...
Ever lost points on a test because you forgot to write the units? Rightfully so! Numbers have no meaning without their units of measurement. Two can be greater than 12. Three can equal one. This is all dependent on the unit of measurement being used. In your general chemistry class, you will encounter measurements of all sorts. These measurements ...
Imagine this...you’re taking your general chemistry midterm and you’ve decided to shuffle through the exam and complete all the hard things first. You’ve totally underestimated how much time those problems were going to take you and now you have three minutes left to write the electron configuration of 10 elements. Untimed, this would be easy to ...
Formal charge is the charge that a bonded atom would have if its bonding electrons were shared equally. Note:
I’ve already covered how to easily manage carboxylic acid derivative formation and manipulation using the Reactivity Hill. Say we’re tired of whatever derivative we just created and want to bring the derivative back to its parent acid (the particular acid the derivative came from). There are two ways to “take home” any acid-derivative. We can ...
Although some people genuinely enjoy it, organic chemistry is stigmatized as the bane of every science major's curriculum. Before you actually take one or two courses in this subject, the horror stories that you've heard from those who have already taken these courses fill you with anxiety and leave you fearing the unknown. I'm not going to sugar ...
If you haven't read Part 1 of this blog, please do so now.
Nuclear magnetic resonance spectroscopy, or NMR, is a fundamental analytical technique used by chemists to determine the structure of organic compounds. Unlike other analytical techniques, such as infrared spectroscopy or mass spectroscopy, NMR allows for the complete interpretation of molecular structure and can be quantitative.
Your professor gives you the below molecule. Can you quickly determine the hybridization of every atom? Determining and understanding hybridization in Orgo 1 isn’t a futile practice. It’s an idea key to understanding mechanism and reactivity all the way through Orgo 2. Thankfully, the rules of thumb used to determine an atom’s hybridization are ...
A common exam question that comes up in both Orgo 1 and Orgo 2 requires students to determine a reaction’s equilibrium position. The question usually looks something like this:
We all know Orgo 1 professors love stereoisomers. Consider the equation A + B = C. Most professors expect you to fill in the question mark with all possible products and then indicate the major product(s), while other professors may provide you a potential C and then ask you if the statement is True or False.