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SEEKING A SCIENCE TUTOR? NEED TO CONTACT THE WEBSITE CREATOR? You can contact me through the phone number above or my e-mail: andrewscientifictutor@gmail.com I charge $60 an hour for all my online or in person tutoring. NO EXCEPTIONS. My name is Andrew and I live in the SAN DIEGO, CA area. I tutor science, in person, in the San Diego area or I can tutor over the internet anywhere in the world. If you would like to see my resume click on this…

What are Boyle’s Law, Charles’ Law, Gay-Lusac’s Law, Combined Gas Law…? I call these the dynamic gas laws because dynamic means changing and some kind of change is exactly what these gas laws are describing. These laws are meant to be useful when you have some kind of container of gas at certain conditions (of pressure, volume, moles, and temperature) and then several minutes or seconds later you change some of the…

What are empirical and molecular formulas? VIDEO Explanation of empirical and molecular formulas This part of the lesson is understanding what chemistry books call the empirical and molecular formula. In terms of definition, the empirical formula is the simplest ratio of atoms in a compound written in subscripts. The molecular formula is a true number of atoms in a compound written in subscripts. I am not really concerned that you know these…

What is the ideal gas law? The ideal gas law is an equation. What the equation describes is how you can manipulate different factors to control how a gas behaves. There are 4 factors in the ideal gas law ; pressure, volume, moles, and temperature. I have already explained pressure in the previous section so here I will give a brief description of volume, moles, and temperature. Volume is how much space something takes up. Moles are how many or…

How is the empirical and molecular formula linked to the molar mass? Another way that empirical and molecular formulas can be asked about is in terms of comparing their molar masses. Lets try that example we had before where the molecular formula was N4O10 and the empirical was N2O5. What is the molar mass of the molecular formula? It is approximately 216g/mol. What is the molar mass of the empirical formula? It is approximately 108g/mol. If we…

COLLEGE: RELATIONSHIPS BETWEEN ACID AND BASE EQUILIBRIUM CONSTANTS (Ka and Kb): When you are given multiple Ka or Kb values (like Ka 1 , Ka 2 , Ka 3 ), you can also combine them together into an overall Ka or Kb by multiplying them together. The equations below display what I mean.   Ka = Ka 1 * Ka 2 , * Ka 3 Kb = Kb 1 * Kb 2 * Kb 3   Examples : Solve for the overall Ka or Kb value below   If Mg(OH) 2 has a Kb 1 of 0.3 and a Kb 2…

How do you get the empirical formula from the percent of each element?   VIDEO Empirical and Molecular Formula Demonstrated Example 3 : What is the empirical formula if the compound has a mass that is 60% oxygen and 40% sulfur? Use this periodic table if needed.   What is all the information we are given?   Answer: 60% Oxygen = 0.6 40% Sulfur = 0.4   For the next step we have to take a leap of imagination. Let us pretend…

What is Effusion? Effusion and Diffusion are very similar. Diffusion is the movement of particles or molecules across one or more barriers with tiny holes in it. Effusion is a simplified type of Diffusion. That is, effusion is the movement of particles or molecules through only one hole between only two containers. Here is a video demonstration. Regardless , you do not really have to know any of that to succeed in this section. The equation for…

What is STP? STP stands for the Standard Temperature and Pressure. It should be more correctly named the standard temperature and pressure of human inhabitants on earth. That is to say it is approximately the average of the pressure and temperature that most humans live at during most of their lives. The standard temperature is 0 C or 273 K and the standard pressure is 1 atm or 1.013 * 10 5 Pa. To put that into perspective, the standard…

How do you get the empirical formula from the mass of each element? Other types of empirical and molecular formula problems require you to take the mass of each element and form them into an empirical formula. Remember the mass in grams can always be converted to the moles of a chemical or element if we know which chemical or element we are talking about. This conversion between mass and moles was taught in the previous section on how to…

How do you calculate the radioactive half-life? Radioactive hal f-life can be used to describe how old something is by measuring how much of a particular isotope is remaining after a certain amount of time . The mathematics of how radioactive decay works can be a little confusing. If you went over the integrated rate law section , then you will know the calculations coming up are called first order equations. If you did not go over this section…

What causes the periodic trends? VIDEO Explanation for cause of Periodic Trends To ask about why the periodic trends exist is to ask a very fundamental question about how the structure of the atom and the structure of how the universe itself is put together. To understand we start off with what is called Coulomb’s Law. Coulomb’s Law is an equation that describes one of the few forces that holds our universe together (similar to…

What sections should I know before attempting to learn this section? –-> Equations   How do you solve for an unknown? Besides multiplication and division, the most important mathematical skill you will need for this class is the ability to perform algebra manipulations to solve for an unknown variable like “x”. It is essential that you learn this skill early on in chemistry and continue to excel at it throughout the class. It is also…

How do you balance a chemical equation? The next step is to balance entire chemical equations. Balancing chemical equations comes from the concept that the amount of stuff you put into the reactants side of the chemical equation should be the same amount of stuff you get out of the products side of the chemical equation. Another way that chemistry books and teachers usually say it is that mass is not gained or lost in a chemical equation. It is…

HOW DO WE CALCULATE Δ G (Second Way)? The second way to calculate Δ G is to use a formula that involves enthalpy, temperature, and entropy. The formula is below:   Spontaneity = Enthalpy – (Temperature * Entropy) Δ G = Δ H – (T * Δ S)   Δ G is in the units Joules (J). Δ H is in the units of Joules (J). T is in the units of Kelvin (K). Δ S is in the units of Joules per Kelvin (J / K). However, again because all of these are…

What is the reaction quotient? The reaction quotient is often explained in a very confusing manor. However, it is something quite simple. The reaction quotient allows you to compare the current concentrations or pressures of the reactants and products to the eventual equilibrium they will achieve . This gives you a hint as to which way or how the equilibrium will shift. Very similar to Le Chatelier’s Principle. How do we figure out the…

How do you compare the ionic radius (ionic size) of two or more atoms? Ionic radius is really the same as atomic radius with some modifications. Here the ionic radius table is not very important for solving possible problems you will encounter on a test, but it does give you a good idea of how the atomic radius changes as you take a non-charged element and turn it into an ion. The ionic radius describes how the radius or size of an atom…

What sections should I know before attempting to learn this section? —> Solving for an Unknown —> Calculating the Wavelength and Frequency of Light   How do you calculate the energy of light? We can also link the frequency calculations to the energy of a wave of light. When the frequency of a wave is HIGH the energy is LARGE. If the frequency is LOW the energy is SMALL. This relationship is also in the equation below….

What is percent yield? The percent yield section is very simple mathematically. However, the components of the math equation for this section are often not clearly labeled. On top of that, percent yield will quite frequently be mixed in with other concepts like stoichiometry. In light of this, I will try to show a clear definition of the percent yield equation and give examples that are mixed with other concepts. The equation is below. Percent…

What is the lesson about? This lesson is about how gases behave. It allows you to define them in terms of several characteristics. It also teaches you about more simple definitions like pressure and temperature and more complicated situations like how gas can change under different conditions like temperature.   Why is it critical to understand? Learning how gases work prepares you with information for later lessons like reaction rate,…

What is the nuclear binding energy? Where does the energy of fusion and fission equations come from? We ll, s o far we have been treating the masses in nuclear equations as whole numbers. However, if you become super accurate at measuring the masses of different isotopes before and after a nuclear reaction, you will start to notice something strange. If you take two light elements and smash them together to make two heavy element s, t here is a…

What is the Kinetic Molecular Theory? This is a review of the subject but for a more complete explanation also check out the molecules and states of matter section in the states of matter lesson. To understand gasses, we must first understand what is called the kinetic molecular theory. What is the kinetic molecular theory? Let us break down the phrase. KIN means movement, MOLECUL means molecule. It is a theory of how molecules move. This…

    What should you know before attempting this lesson? If you have trouble in this lesson go back to sections on definition and layout of a chemical equation, coefficients, using stoichiometry in conversions, and Molarity.   New Learning Sections:   —> Definitions of Reaction Rate and Using Reaction Rate Stoichiometry —> What the Reaction Rate Looks Like on Graphs —> Defining and Writing the Rate…

  Some of you may have noticed that the molar mass (or atomic mass) can be written in terms of a ratio. This means we can use it as a conversion. If your molar mass of CH4 is 16 g/mol that means we can write it as a ratio like the ones below.   16 g 1 mol or 1 mol 16 g   Either way, both are true statements of the relationship between grams and moles of CH4. That means you can write the molar mass for a conversion whichever way…

What sections should I know before attempting to learn this section? —> Introduction to Units —> Unit Prefixes —> Introduction to Problem Solving   How do you solve density word problems? To help further your problem solving skills, I will introduce you to the concept of density. Density is the mass per unit volume. Another way to state that is the mass divided by the volume. See equation below: Density = mass…

HESS’ LAW:   PAGE IS NOT YET COMPLETE   Hess’ Law is an idea that you can add or summarize multiple chemical equations together to learn about the overall enthalpy or energy information about them. However, this addition of equations is not the usual addition that you are used to. We have to manipulate the chemical equations and their enthalpy through multiplication, division, and reversal of signs (positive and negative)….

What is the difference between covalent, ionic, and metallic bonds? Two or more elements are held together by their electrons, but the electrons can do this in different ways. Electrons are like the skin of the atom because they are on the outer parts of the atom. Atoms interact with each other mostly by contact or trading of electrons, just like people interact with each other by contacting skin in the form of a handshake. As you read through…

How do you use concentration values in equilibrium equations? What is the equilibrium constant Kc? Now that we are done writing equilibrium equations we can start using them with the molar concentration numbers and determine what numbers or values we have. If a book or teacher mentions an equilibrium problem where you have molar concentrations (Molarity) then they will sometimes call the equilibrium constant K c (or Keq) . C is refering to the…

These values are valid for the Temperature 25 C. Chemical Substance (state) ∆Gf ◦ kJ/mol Ag(s) 0 Ag+(aq) 78 AgBr(s) -100 AgCN(s) 164 AgCl(s) -110 Ag2CrO4(s) -622 AgI(s) -66 Ag2O(s) -10 Ag2S(s) -40 Al(s) 0 Al2O3(s) -1580 Al(OH)3(s) AlCl3(s) -630 Ba(s) 0 BaCl2(s) -790 BaCO3(s) -1138 BaO(s) -552 Ba(OH)2(s) BaSO4(s) -1354 Be(s) 0 BeO(s) -570 Be(OH)2(s) -815 Br2(l) 0 Br2(g) 3 Br2(aq) 4 Br–(aq) -105 Cd(s) 0 CdO(s) -230 Cd(OH)2(s) -474 CdS(s)…

How do temperature conversions work? If you want to know more about temperature go back to the temperature section in the states of matter lesson . What you need to learn from this section is how to convert between the temperature scales (units to measure temperature). Because temperature devices were so difficult to make until about 190 0, different people came up with different temperature scales. As a resul t, we are left with some…

What sections should I know before attempting to learn this section? —> Introduction to Units —> Unit Prefixes —> Introduction to Problem Solving   What about more advanced metric unit conversions? We want to use the units and ratios we discussed in the previous section as mathematical tools for conversions. I will show you how to do one example problem of each of the three ratio techniques. Keep the unit…

What sections should I know before attempting to learn this section? —> Solving for an Unknown   How do you calculate the wavelength or frequency of light? In addition to the wavelength and frequency being related to the color of light, they are also related to each other. If you have a LONG wavelength then the frequency is LOW and if you have a SHORT wavelength then the frequency is HIGH . This relationship is also demonstrated…

What skills do I need before I start predicting the products of a precipitation reaction? Forming the products of a precipitation reaction requires bringing together a lot of different previous skills you have learned in your chemistry class or on this website. The primary sections you need to know or should review are how to form ionic compounds and how to break apart ionic compounds and balancing chemical equations and types of chemical…

  Percentages are very useful in chemistry. A percent is used in chemistry usually when we are trying to dissect something that has multiple parts. We describe each part as being a percent of the total. The percentage should always be the same even when we are dealing with a small or large amount of the same thing. Let’s go through an example.   Examples: If a 100-box crate of ice cream is delivered to the ice cream store on a slow…

What sections should I know before attempting to learn this section? —> Representation of Compounds and Molecules with Subscripts —> Covalent, Ionic, and Metallic Bonds —> Introduction to Polyatomic Ions Part 1 —> Forming Ionic Compounds   How do you break apart ionic compounds? As we go forward into the future of learning chemistry it will become essential for us to be able to take ionic compounds and…

    When you compared the oxygen to the sulfur in a mole ratio, you came out with a nice, neat number like 3. This doesn’t usually happen, but because I wanted you to focus on the process and not the exact numbers, I made a simpler problem for you. However, if you are comparing mole ratios and you come out with a number like 2.98 or 3.05, then you can safely assume it rounds off to 3. If you happen to come out with a number like…

What is specific heat capacity? Energy or heat energy can also be involved in changing the temperature of a substance. Although it is not essential to know more about what temperature is for this section or lesson, you can review it in this link on temperature if you wish. The relationship between energy and a substance’s temperature is described by the equation below:   Heat Energy = Mass * Specific Heat * Change in Temperature 1 Q…

What is the heat of fusion and heat of vaporization? In the previous section of specific heat capacity we only discussed and did calculations for how energy affects subst ances within the same state (gas, liquid, solid) to change their temperature . However, in this section we will discuss how to use energy to cause chemical substances to go from one state to another (example: solid to liquid). This is called the heat of fusion or heat of…

What is the lesson about? This lesson is about how to convert between the different measurements that are very commonly used in chemistry. Just like in your daily life, you convert between common things like time and distance. How long does it take you to get the class or work? Well, if it is 15 miles away then it may take you 20 minutes to get there. Now if you ask the question,” what time should you get up?” Then the 20 minutes is going to be…

How are chemical equations organized? Chemical equations are a series of elements or compounds that when added together under the right conditions cause a chemical reaction to happen and produce a new arrangement of elements or compounds. Those elements do not change, but their bonds to other elements can.   Examples:   H2 + O2 —-> H2O   NaCl + MgBr2 —-> NaBr + MgCl2     The chemical equations also…

What sections should I know before attempting to learn this section? —> Protons and Electrons —> Neutrons —> Isotopes —> Periods, Rows, Columns, and Groups —> Ions —> Atomic Notation Part 1 How do I use the periodic table to produce element with atomic notation? In this section YOU WILL HAVE TO USE THE PERIODIC TABLE as a reference . Now that we have tackled the atomic notation part one…

  We can further expand our understanding of stoichiometry by using the system of ratios we have created as conversions for questions that we are asked in chemistry. This section builds on the skills you have practiced starting in the unit conversions section and continued in the grams moles molecules and atoms lesson. These questions may seem strange to some students, but we use them in everyday activities. Baking and cooking are the best…

What sections should I know before attempting to learn this section? —> Covalent, Ionic, and Metallic Bonds —> Forming Ionic Compounds —> Breaking Apart Ionic Compounds —> Introduction to Polyatomic Ions Part 1   How do you use an ionic name to create the ionic compound with transition metals? Now let’s try to reverse the question of the problems. Given the chemical formula come up with the name of the…