Chemistry 107 Exam 1

How I Actually Survived Chemistry 107 Exam 1

Chemistry 107 Exam 1 covers the first six to eight weeks of General Chemistry. That means atomic structure, the periodic table, bonding basics, stoichiometry, chemical reactions, and sometimes an introduction to gases or thermochemistry depending on the school. It sounds manageable. It isn't. The exam is a filter designed to separate people who can manipulate symbols from people who actually understand what those symbols represent. The biggest mistake I see students make is studying for Chemistry 107 Exam 1 the way they studied for high school chemistry. High school chemistry rewards memorization. College chemistry rewards pattern recognition under time pressure. If you only memorize formulas without understanding their boundaries, you will freeze on the second half of the exam.

Chemistry 107 Exam 1: What Actually Shows Up

Stoichiometry is always there. Molar mass calculations, limiting reactant problems, percent yield, and empirical formula determination. These questions appear in multiple formats. Some are straightforward number crunching. Others are word problems disguised as chemistry problems. The limiting reactant questions are where most students lose points, not because they don't know the method, but because they rush through the mole ratio step and pick the wrong substance as limiting. Bonding questions test whether you can predict molecular geometry using VSEPR theory and determine polarity from that geometry. This is where students who skipped lectures struggle. You cannot memorize every possible molecule. You need to understand why tetrahedral geometry with four identical bonds produces a nonpolar molecule while three bonds and one lone pair on the central atom creates a polar trigonal pyramidal shape. Gases, if they appear, usually mean ideal gas law calculations and sometimes Dalton's law of partial pressures. The ideal gas law itself is simple. PV equals nRT. The trick is knowing which variables change and which stay constant between two states. Students routinely plug numbers into PV equals nRT without checking whether they actually have all four variables in consistent units. Pressure in atmospheres, volume in liters, temperature in Kelvin. If your temperature is in Celsius and you forget to convert, your answer will be wrong by roughly three percent. That single mistake costs more points than most students expect.

My Actual Strategy for Studying

I stopped trying to reread the textbook after the first midterm. Rereading gives you a false sense of competence. You recognize the material and confuse recognition with retention. Instead I did practice problems under timed conditions. Not practice problems with the answers open. I closed the book, set a timer, and worked through end-of-chapter problems and any old exams the professor had posted online. The specific problem that made me change my approach was a stoichiometry question that asked for the mass of product formed when a certain volume of gas at non-standard conditions reacted with a solution of known molarity. Most students immediately tried to convert the gas volume to moles using 22.4 liters per mole. That only works at STP. The question gave you a temperature and pressure that were clearly different. I lost points on that exact type of problem on a practice quiz and then refused to make the same mistake again. The workaround is simple but easy to overlook. Use the ideal gas law to find the moles of gas first. PV equals nRT rearranged to n equals PV over RT. Once you have the moles, the rest is standard stoichiometry. For bonding and molecular geometry, I drew the Lewis structures for every molecule listed in the study guide, then determined the electron geometry, the molecular geometry, and the bond angles. Doing this mechanically removes the guessing. If you draw the structure correctly, the geometry follows directly from counting electron domains around the central atom. Four domains is tetrahedral geometry with 109.5 degree bond angles. Three domains with one lone pair becomes trigonal pyramidal. Two lone pairs make it bent. The pattern repeats for five and six domains.

Things Nobody Tells You About This Exam

The periodic table provided on the exam usually includes atomic masses to two decimal places. Some professors provide a simplified version with fewer digits. Using the rounded masses instead of the precise ones can shift your final answer in multi-step stoichiometry problems. It rarely changes the first decimal place but in grading curves that are tight, that difference matters. Always check what your professor provides and use exactly those values. Significant figures matter on Chemistry 107 Exam 1, and professors enforce them differently. Some deduct a full point for every answer with the wrong number of sig figs. Others barely notice. I once had a professor who gave partial credit but wrote a small note on every wrong sig fig answer. By the end of the exam, the notes added up to a missed letter grade. Another professor ignored sig figs entirely and focused purely on the calculation method. The only way to know which version you are dealing with is to check past exams or ask in class early. Do not find out on exam day. Here is a counter-intuitive point about limiting reactant problems. Many students assume the reactant with the smallest number of moles is the limiting reactant. That is almost never true. The limiting reactant is the one that produces the smallest amount of product based on the balanced equation. A reaction might have 0.5 moles of one reactant and 0.2 moles of another, but if the stoichiometric ratio requires four moles of the first for every one mole of the second, the first reactant is still the limiting one despite having more moles initially. Write out the mole ratios explicitly before declaring a limit.

Common Pitfalls That Cost Real Grades

Empirical formula problems require you to convert mass percentages to moles and then divide by the smallest mole value to get whole number ratios. The pitfall is rounding too early. If your ratio comes out to 1.33 for one element and 2.67 for another, multiplying by three gives you the whole numbers. Students often round 1.33 to 1 and 2.67 to 3, producing the wrong formula entirely. Keep extra digits through the division step and only round at the very end. Thermochemistry questions involving enthalpy changes use Hess's law when multiple reactions are given. The trick is that you can reverse reactions and multiply them by coefficients, and you must do the same to the delta H values. I watched a student reverse a reaction but forget to change the sign on delta H. That reversed the final answer completely. Write the original and modified equations side by side. Track every coefficient and every sign change explicitly. It takes ten seconds extra and saves you from a careless error.

What This Study Method Does Not Do

Timing yourself on practice problems does not teach you the underlying concepts. If you are working through problems without understanding why a step exists, you will hit a wall when the exam throws a variant you have never seen. The practice problems are for building speed and catching calculation errors, not for learning the material from scratch. Read the textbook chapters or watch lecture recordings first. Then use timed problem sets to lock in the procedures. This approach also assumes you have access to practice materials with answer keys. If your professor does not provide old exams or solution sets, studying becomes significantly harder. In that case, use the back-of-chapter problems and work through them slowly without timing. Speed comes later. Understanding comes first. For Chemistry 107 Exam 1 specifically, focus your energy on stoichiometry and gas law problems. Those topics carry the most weight and the most opportunity for easy points if you can execute them cleanly under pressure. Bonding and gas questions are straightforward if you have drawn enough Lewis structures. The exam will not punish you for knowing the concepts. It will punish you for rushing through the math.