CHEM 1500, Study Guide
CHEM 1500, Study Guide CHEM 1500
Popular in Concepts in Chemistry
Popular in Chemistry
This 4 page Study Guide was uploaded by D Holley on Friday September 16, 2016. The Study Guide belongs to CHEM 1500 at Ohio University taught by Corey Beck in Fall 2016. Since its upload, it has received 47 views. For similar materials see Concepts in Chemistry in Chemistry at Ohio University.
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Date Created: 09/16/16
Study Guide CHEM 1500 8/239/15 When I’m studying, I like to tackle all the materials I know best, usually the ones I learned most recently. During week four we learned AZX Notation and Atomic Mass, we also took a quiz. AZX Notation is how we are going to identify each number of protons, netrons and electrons in a specific atom. We denote this as X with the different letter scripts. A is in the upper left corner, Z is in the lower left corner and C is in the upper right corner. X=Atomic symbol (found on periodic table). A=Unique number of protons in the specific atom. Z=Mass number (sum of protons and neutrons). C=The charge of the atom (difference of protons and neutrons). Next we learned about the Atomic Mass. COMPLETELY DIFFERENT FROM THE MASS NUMBER. The atomic mass if also found on the periodic table and contains a number of decimal points. The atomic mass is measured in Atomic Mass Units (AMU). It is the weighted average of the present isotopes in the specific atom. Of course it comes with an equation: AM=[%Abu_a/100%]AMU_a+[%Abu_b/100%]AMU_b… This is an experimental value. The abundance (Abu) is majority of the sample of the whole element. So, since this information was the freshest, I’d go over it first, then onto the next most recent material. Week three we got into the mathematically difficult solving; Dimensional Analysis and Temperature. Dimensional analysis is used in all countries, but every country uses different units and this is why it’s so handy. We will always be multiplying by a conversion factor. Some of the conversions you will know by heart and others are provided to you on that handy two chart you should’ve printed out or downloaded onto your phone. Again, don’t forget the significant figures, they are leaving any time soon. Usually when solving with dimensional analysis you will feel the need to cross multiply. This works great for one step conversions, but you should never get into the habit of doing it. We know that the units in the original problem will have to be canceled out with units on the bottom of the conversion factor, so you could think of that as cross multiplying. Then, we began talking temperature. Dr. Beck gave us three equations that are related to temperature, but he is only going to provide two of them on our quizzes and exams, that is why it is important that you play around with these equations and know how to reverse them. The first equation relates degrees Fahrenheit (˚F) to degrees Celsius (˚C): T(˚F)=9/5T(˚C)+32. The second equation relates degrees Celsius (˚C) to Kelvin (K): T(K)=T(˚C)+273.15 Those two equations will be provided on the quizzes and exams, if needed. ˄ ˄ The third equations, which is derived from the first equation I listed, is T(˚C)=5/9(T(˚F)32). You can obtain this equation by using algebra. We have two significant temperatures that come in handy: freezing and boiling. We know that the freezing point of water is 32˚F and 0˚C. We also know that the boiling point of water is 212˚F and 100˚C. You do not have to memorize these, but they could help you give yourself a few extra minutes on an exam. There is something special about the Kelvin scale. We call the Kelvin scale the absolute scale because when Kelvin is 0 we have predicted that all molecular movement has completely stopped. Therefore, 0K is the coldest temperature that can be recorded. Don’t forget to be keeping up with the weekly videos/quizzes, homework and make sure you’re working through practice problems throughout each week! In week two we covered three main topics: density, significant figures and calculations of significant figures. We focused on significant figures (sig figs, SF) and ran over the basis of density. Let’s start with density. Only a brief overview. Density is referred to as the ratio of a mass and a volume. As chemists, scientists and engineers we can use that to create a formula: d=m/v. That is density equals mass over (divided by) volume. The units for density have to be related to both units of mass and volume and will always be mass over volume (m/v). Ex. g/mL. The one density you should know is the density of water (dwater=1g/mL). In Chemistry we will be using this density to relate to all others. Density is also referred to an intensive property, but mass and volume are extensive properties. Well, what the heck is that. An intensive property has nothing to do with the amount of the material and there for there will be no change. Meaning if we have a cup of water that’s density is 1g/mL, then the swimming pool in our backyard has the density of 1g/mL. An extensive property is the exact opposite; the mass will change if the amount of the material changes, as well as, the volume. Since d=m/v and d is an intensive property, m/v must also be intensive. Now for Significant Figures. First, let’s go over the rules for using sig figs: All nonzero digits are significant figures: 1, 2, 3, 4, 5, 6, 7, 8, 9. All leading zeros are not significant figures, even if a decimal is present. In mathematics we read our numbers left to right and any zero read before a nonzero digit will not be a significant figure. All captive zeros are significant figures: 1004, 20005, 403, etc. Captive zeros are withheld between two nonzero digits that are ALWAYS significant. Trailing zeros are only significant figures if a decimal is present: 644.00. Significant figures are used to identify how precise and accurate a measured value is. Every instrumentation in a Chemistry laboratory will have a given set of sig figs. Whenever we are dealing with significant figures in this class, you ALWAYS have to RECORD the number of sig figs in each calculation at the end. Significant Figure Calculation On top of all the general rules of significant figures there are two separate rules for performing multiplication/division and addition/subtraction. Multiplication/Division: Depends on the number of significant figures being multiplied or divided. After undergoing the process, take the least number of sig figs present in the initial problem. Ex. 3.4*2.111, 3.4 has two sig figs and 2.111 has four sig figs, so after multiplying the two you would make the product have two significant figures because two is the least of the initial problem. Addition/Subtraction: Has nothing to do with significant figures. Depends on the number of available decimal places of each number being added or subtracted. Like multiplication and division the final solution will take form of the least of the initial problem. Ex. 3.4+2.111, 3.4 have one available decimal place and 2.111 has three available decimal places, so the sum of the two will have one available decimal place. dp=decimal place. You ALWAYS have to keep tract of the significant figures during each process of a complex problem. You CAN NOT DROP the insignificant figures after establishing the significant figures, this will skew the data on a large scale. Use PEMDAS to perform the processes in the correct order and keep tract of the correct number of significant figures. Lastly, but firstly, week one was mainly a “Show What You Know Week”. Tuesday was an introduction. We had to watch a video for Thursday and we took a skills exam. The video was a short piece about PEMDAS. Dr. Beck explained the meaning and what you can do with it. You probably learned certain sayings for this and that’s great. Do what you can to memorize this process, we will be using it all semester to solve problems in this class.
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