Most students study for Gen Chem by rereading notes and rewatching lectures, then walk into the exam and freeze on the first problem that looks unfamiliar. By the end of this post you will know how I look at every Gen Chem problem, how to map your way from the question to the answer, and the one "hack" that actually makes test day easier.
Every Problem Is a Rubik's Cube
Here is my perspective: each question is like a Rubik's cube. There are thousands of different iterations, but each can be solved the exact same way with a given set of algorithms. The scrambled cube is the conditions, numbers, and context given in the question. The end goal is the solved cube. The real problem is figuring out which algorithms (formulas or conversion factors) you need to use, and in what order. Once you get that done, there is no such thing as a harder problem, just one with more steps.
Build a Problem Road Map
I visualize test problems as a problem road map. Where am I, where am I going, and how do I get there? If I am solving a problem where two volumes of solution with differing molarities are combined in a reaction, and I am determining the theoretical yield of the product, then I know I need to go from M of reactant to moles of reactant using M = mol/L. Then I convert moles of reactant to moles of product using the stoichiometric coefficients, which lets me compare yields to determine the limiting reagent. Then I use molar mass (g/mol) to convert the moles of product produced from the limiting reagent to theoretical yield in grams.
Here is that exact road map with real numbers.
The problem: 50.0 mL of 0.200 M silver nitrate (AgNO₃) is mixed with 50.0 mL of 0.150 M sodium chloride (NaCl). Silver chloride (AgCl) precipitates out. What is the theoretical yield of AgCl in grams?
AgNO₃ + NaCl → AgCl + NaNO₃
| Step | Where am I? | Tool (the "algorithm") | Result |
|---|---|---|---|
| 1 | Molarity of AgNO₃ | M = mol/L, so mol = M × L | 0.200 × 0.0500 L = 0.0100 mol AgNO₃ |
| 2 | Molarity of NaCl | mol = M × L | 0.150 × 0.0500 L = 0.00750 mol NaCl |
| 3 | Moles of each reactant | Coefficients (1:1 for both) | AgNO₃ could make 0.0100 mol AgCl; NaCl could make 0.00750 mol AgCl |
| 4 | Two possible yields | Smaller one wins | NaCl is the limiting reagent: 0.00750 mol AgCl |
| 5 | Moles of AgCl | Molar mass of AgCl, 143.32 g/mol | 0.00750 × 143.32 = 1.07 g AgCl |
Notice that nothing in that problem is hard. Each step is one tool you already know. What makes it feel hard on a test is not knowing which tool comes next. That is what the road map fixes. Before you touch your calculator, write the route across the top of your page:
Mmolmol productlimiting reagentg
Then fill it in.
So, What Is the Hack?
So, what is the hack? Practice. The intuition of understanding how to get from start to finish is earned through repetition and memorization. No one gets great at mental math without first memorizing multiplication tables. No one gets great at reading out loud without spending a great deal of time sounding out words phonetically. It is no different in this circumstance. You must practice and memorize.
What Putting In the Reps Actually Looks Like
Not all practice is equal. Reading a solved example and nodding along is not a rep. A rep is you, a blank page, and a problem you have to finish on your own. Here is how I would spend a study week before a Gen Chem exam:
- Memorize the toolbox first. Make one page with every formula and conversion factor from the chapter: M = mol/L, molar mass, the ideal gas law, whatever your unit covers. If you have to look it up during practice, you do not know it yet.
- Sort problems by type. Go through your homework and old quizzes and label each problem: dilution, limiting reagent, percent yield, gas law, and so on. You will find there are fewer types than you thought.
- Write the road map before you calculate. For every problem, write the route first (start, tools, finish). If you can write the route, the math is the easy part.
- Work without your notes. Close the book, set a timer, and solve. Then check. The problems you miss are the ones worth your time.
- Redo your misses two days later. If you can solve it cold after a break, you own it. If not, it goes back in the pile.
- Mix it up before the exam. Your test will not tell you which chapter a problem came from. In the last few days, shuffle problem types together so you practice recognizing which road map you need.
Do this and the exam stops being a collection of strange new problems. It becomes a set of cubes you have already solved, just scrambled a little differently.
Use YouTube and AI for the "Why"
The learning environment has significantly changed in the last decade, and more so in the last couple of years. With YouTube and AI available, there are educational resources at the touch of a button. But the key is not to use them merely to find the right answer, but to solidify the "why" behind the answer. When it comes time for a test, only the content that you drilled over and over again will remain at the front of mind. So make the sacrifice and put in the reps.
A couple of prompts that put AI to work for understanding instead of answers:
- "Here is my work on this problem. Don't give me the answer. Tell me which step went wrong and why."
- "Give me three new problems that use the same road map as this one, with different numbers. Don't show the solutions until I ask."
Frequently Asked Questions
How long should I study for a Gen Chem exam? There is no magic number, but start at least a week out and study in short daily sessions rather than one long night. Repetition across several days is what moves a formula from "I've seen this" to "I know this."
Is it better to memorize formulas or understand them? Both, in that order. You cannot apply a formula you don't remember, and you will not know when to apply it unless you understand what it does. Memorize the toolbox, then practice until you know when to reach for each tool.
What should I do when I see a problem I have never seen before? Draw the road map. Write down what you are given and what you are asked for, then ask which tools connect the two. Most "new" problems are familiar steps in a new order.
Need a Second Set of Eyes?
If you have done the reps and something still is not clicking, that is exactly what a tutor is for. I tutor General Chemistry I and II in person in Johnson City and online, and every new student starts with a free intro session where we work real problems from your course. Learn more about Gen Chem tutoring.