Overview
The first laboratory exam covers experiments 2 (Measurements), 3 (Properties of O2), 4 (Properties of H2), 5, (Specific heat), and 6 (Freezing points / graphing). To prepare for the test, the first thing you should do is go back and read the write-ups in your lab manual. Don’t just read the answer sheets!
You’re responsible for these experiments:
- Experiment 2: p 11-22
- Experiment 3: p 23-32
- Experiment 4: p 33-42
- Experiment 5: p 43-49
- Experiment 6: p 51-59
The lab exam should take you about an hour. There will be several types of questions – there may be multiple choice, fill in the blank, and a few short (a sentence) answer questions. Bring a calculator, since there will be problems to solve on the exam.
Test Format
The lab test is a written test, much like one of the CHM 101 lecture tests. Expect approximately 30-50 questions. Questions types may be: multiple choice, fill-in, short answer, or problem.
Specifics
General: You should know about lab safety and the safety equipment we have in our lab. See pages ix-xi in your lab manual for more information. You should also be able to identify the common laboratory equipment shown on pages xii and xiii of the lab manual.
Experiment 2: For the measurements lab, you should be
familiar with the concept of significant figures. Be able to read the scale off a ruler / graduated cylinder to the correct number of significant figures. Be able to add, subtract, multiply, and divide measurements while keeping the correct number of significant figures. Be able to find density from measured mass and volume data as you did during the first experiment. Have a working knowledge of the Fahrenheit and Celsius temperature scales. You don’t have to remember the equations for converting back and forth (they will be provided), but you do need to know how to use them. Be able to use dimensional analysis to perform unit conversions. Be able to determine whether measurements are accurate or precise using appropriate data. The concepts we learned in this lab are important for all future labs, so I expect you to know them well.
Experiment 3: For the oxygen lab, you should know the molecular formula (O2) and atomic symbol (O) of oxygen. You should know how we generated it in our lab (decomposition of H2O2 to form water and oxygen) and how we collected O2 in our bottles. What was MnO2 used for? Know that oxygen is denser than air and that it supports combustion. Know what combustion (burning) is – reaction of something with oxygen to produce heat and a flame. Know that the products of combustion are oxides (compounds containing oxygen and one other element). Know that the more oxygen is present, the faster combustion takes place. Be familiar with the results of the tests we did: glowing splint, burning sulfur, burning magnesium
Experiment 4: For the hydrogen lab, you should know the molecular formula and atomic symbol of hydrogen, and that it is lighter than air (that’s why we had to keep the bottles upside down!). Know what happens when you drop sodium in water. Know what happens when you react a metal and a dilute acid (hydrogen is produced along with a salt). Be able to describe how hydrogen was prepared in the lab and how it was collected. Know that hydrogen is combustible (it burns), but that it does not support combustion. Know that when hydrogen burns, it produces hydrogen oxide (water). Be familiar with the results of the tests we did: burning splint,sodium in water.
Experiment 5: For the specific heat experiment, you should be able to calculate heat given information on a sample’s mass and temperature change. Be able to describe the setup for this experiment. Why was the metal heated in a dry test tube? Why was it necessary for the water in the cups to cover the metal? How does the specific heat relate to the atomic weight of a metal? Be able to calculate the specific heat of a metal given data similar to what you recorded in this experiment.
Experiment 6: For the freezing point experiment, you should be familiar with what freezing and melting are – and that freezing releases energy while melting requires energy. Know that the liquid state is more energetic (has more energy) than the solid state. Know what supercooling (formation of a liquid that is colder than the freezing point) is and that it can happen in substances that are frozen slowly and without being disturbed. Know what happens to the freezing point of a substance if something is dissolved in it (freezing point lowers). Know how to draw a graph of data given some graph paper (or more importantly, how to read a graph already given to you). Be able to describe the results of each test: freezing with stirring, freezing without stirring (supercooling), and freezing an impure substance.
Board notes
To help you out while studying, here are the notes from the board for each of the experiments on the first lab test: [CHM 101 – Board notes for experiments 2, 3, 4, 5, and 6]