Finding pH

Last Friday we learned about how to find the specific pH of an acid or a base. pH tells how acidic/basic a solution is. We found it by taking the hydrogen ion concentration and putting it into an equation.

The OH- stands for hydroxide ion, what is normally found in bases. It is possible to know the OH- concentration and finding the pH by using these formulas.

Above is a pH scale that gives a few examples of acidic and basic solutions. Solutions form 0-6.9 are acidic and solutions that are form 7.1 to 14 are basic. Pure water is a neutral solution, which is represented by 7 on the pH scale. 

More info and practice:

http://chemwiki.ucdavis.edu/Physical_Chemistry/Acids_and_Bases/Aqueous_Solutions/The_pH_Scale/Determining_and_Calculating_pH

Interactively shows pH: 

https://phet.colorado.edu/sims/html/ph-scale/latest/ph-scale_en.html

Acid Base Solutions

 Yesterday we started a new unit over a different type of solution, acid base. I learned that there are three different models for acid base solutions but we will only learn about two. The first one I knew, it was called Arrhenius acids and bases. Acids have a leading (H+) ion and bases have a (OH-) ion.

The new one I learned was called Bronsted-Lowery Acids and Bases, where during the solution a (H+) ion leaves the acid and goes and is put into the base. These solutions often in equilibrium, so they can occur both ways.

The reason the pairing are attached to "conjugate acid/base" means that when the equation is read the other way (right to left) that they are the acid and base. 

Confuses? Look here for some more info. 

Mass Percentage and Solubility Graph

Mass Percentage is pretty simple, it basically tells you how much solute is in a solution by mass. All you need to find the answer is use this formula.

It's important to remember that when finding the total mass of a solution, that you need to add together the mass of the solute and the solvent. Find some more information here (it also gets into molarity).

Solubility graphs basically tell you when a compound will be saturated, unsaturated, or supersaturated in a solution. Saturation is dependent on the temperature. For the most part, solvents can hold more solute at higher temperatures. Saturation is the point at which a solution of a substance can dissolve no more of that substance. Supersaturated solutions have more solute than can be dissolved in a solution. and unsaturated solutions have less solute than can be dissolved in a solution. If this all sounds confusing to you click here to better understand it.   

Above is a solubility graph, and as you can see, it tells you the saturation point, and that it changes depending on the temperature. With this, you are able to determine if so many grams of a compound will be saturated, unsaturated, or supersaturated in 100 grams of water at any given temperature. 

Molarity

Molarity, also called molar concentration, is a measure of the concentration of a solute in a solution. This is different form moles, that tell you how much elemental entities there is in a chemical substance in regards to 12 grams of pure carbon-12. Although these two subjects are fundamentally different, moles can be used to calculate molarity via this equation:

Molarity seemed like a rather confusing subject at first, but as I saw it more I started to get used to it. if your still confused you can find more information here and here.

Aqueous Solutions

This whole unit is about homogeneous solutions that take place in water. There are two parts to a solutions -- the solvent and the solute. The solvent is the part of the solutions that is present in the largest quantity. The solute is what is dissolved into the solvent. Ionic compounds are mostly soluble, and will disassociate in water. Substances that are not ionic may dissolve in water, depending on their chemical structure. For the most part, if the structure is similar to that of a water molecule, it will dissolve in water.

Ethanol dissolves in water

Substances that do not dissolve in water are generally non-polar in nature. On such example is oil, others being compounds that contain long C-H chains.

Here is some unique features of aqueous solutions, and here is some more information on them.

Murder Lab

This lab was about a theoretical murder case where the victim was poisoned with an unknown chemical. The goal was to find what the chemical was, either potassium iodine or silver nitrate (the victim was violently allergic to potassium iodine and silver nitrate is poisonous when swallowed) and who poisoned the victim.

We found our what the chemical was by combining the mystery solution with sodium carbonate and seeing whether a chemical reaction was caused or not. It did occur so we could assume that mysterious compound was silver nitrate. Then we drained the solution in filter paper and let it out to dry.

All I have to do to complete the lab is find the molarity of the silver nitrate and use that to find the killer.

Post Quiz Regrets

Yesterday we had the first quiz of second of semester, and once again, I probably should had studied before I took it. For the most part I don't think I did too bad because I reviewed my notes the night before, but didn't do any practice and was a little lost on some of the questions. Fingers cross that I do well!

This new unit it about aqueous solutions, solutions that are solvent in water. For the most part it doesn't seem too difficult but I feel that it's going to get harder.