Determination of an Activity Series

 

The purpose of this lab was to determine the oxidation potential of different metals with small scale chemical reaction activity series (basically finding which is more active). The results concluded that the different metals tested (Mg, Zn, Fe, Cu) were not equally active; Magnesium was the most active with four total reactions and a reduction potential of -2.37V, Zinc came in second with three reactions and -0.76 V potential, and Iron (2.87 V) and Copper (0.34 V)  tied for third with 2 reactions. The most reactive to the least seemed to have a connection towards the charge of the reduction potential. The most active, Mg, had the lowest potential while the least active metals had the highest potentials. This is because the negatively charged potentials need electrons. All of these reactions were single replacement and redox reactions. Redox reactions, or oxidation reduction reactions, involve the transfer of electrons between atoms and a change in the oxidation state. A single replacement reaction is when one element is replaced by another. Single replacement reactions are also redox reactions because the transfer of electrons occur with the transfer of elements.

Friday 9/20/13

1. Well this past week has been stressful to say the least. But I am happy to say I have completed the intimidating cation and anion lab along with the rest of the class. I have also completed a quiz, and yet another lab (surprise surprise). So total that makes 11 labs... yay us!
2. It's a proven fact that you learn something new every day. That means a lot of new facts have entered my brain, but the question is which ones stayed? I guess it could be the ways of determining molarity with the titration lab, how to determine net ionic equations, more particle diagrams, and most importantly: to start bringing lab clothes every day :)
3. I believe our class is planning on catching up to our set schedule (hopefully). And also the dreaded ending to Unit 2.. meaning another test... something all of us look forward to. And more than likely many more labs and particle diagrams. YAY science.



http://www.keepcalm-o-matic.co.uk/p/keep-calm-and-calculate-moles/

(our future t-shirts)

Solubility!

Preceding the week long "Separation and Qualitative Determination of Cations and Anions" Lab, we did a pre-lab lab. This mini lab consisted of multiple solutions containing different cations and anions. From the reaction between the different combinations, we determined general solubility rules that helped us in our monster lab. The results below were used to create basic solubility rules:

cations

-all alkaline metals are soluble (Na, K, NH4)

-Lead is always insoluable except for NO3

-Silver is always insoluable except for NO3

anions

-NO3 is always soluble

-SO4 is always soluble except for lead

-Cl is always soluble except for Pb and Ag

-PO4 is generally soluble except for alkaline metals

Mini Titration

According to Bronston and Lowry, an acid is what donates a proton (or H+) in a reaction and a base is the acceptor. All acid-base reactions are neutralization reactions, and produce salt and water. Tirtration is an analytical technique used to calculate the concentration of a solute in a solution. Since we are a bit rusty in our chemistry game, this titration  lab helped us (or me, at least) get back in the swing of molarity. Our goal was to determine the molarity of a dilute solution of sulfuric acid. To do this, we measured 20 mL of the H2SO4 in a flask. Then measured approximately 50 mL of NaOH into a buret. After placing the flask with the sulfuric acid solution onto a magnetic stir plate, 2 drops of phenolphtaleine was added as an indicator. Drops of the sodium hydroxide was added until the solution was a very light pink (not dark pink). This indicated the molatiry of the solution was the same as the 1M NaOH. This took several tries, however (with the execption of Sophia's group, of course). After a couple tries we concluded that it took exactly 18.4 mL of NaOH to neutralize the acid.Therefore, .0184mol of NaOH we used. Then we then multiplied that by the mole ratio of H2SO4 to NaOH, which told us we used .0092 moles of H2SO4. We then divided this by .020L of the H2SO4, giving us the molarity of 0.46M.

Electrolytes & Water

There are four objectives directed towards the lab we did today in class:

1. Review definitions of solution and electrolytes

2. Can you draw a particle diagram of the salt solution?

3. Can you create two different concentrations of salt solutions and qualitatively demonstrate this?

4. Can you mathematically show concentration difference and provide calculations to justify it?

Well I'm not going to lie, electrolytes were not the first thing to pop in my head when you asked about the salt water ( unlike Evan), but of course it did click afterwards; that amazing OOHHH moment happens to me often. Electrolytes are basically compounds that ionizes when dissolved in solvents such as water. A solution is a homogeneous mixture containing two or more pure substances. 

Second comes my favorite thing: particle diagramming! YAY (sarcasm)

The solutions with  different salt concentrations ended up with ratios of 100mL of DI water to 2.5g of salt (salt water) and 600mL DI water to .1g of salt (mimic tap water). We proved this with the electrodes and a light bulb...fun/scary stuff. 

                           original solution (tap water)                                 

                                                                                                                       our solution(tap water mimic)

  our salt water solution

The mathematical part of this pie is difficult to show on a computer... however my calculations were set up like so- 

Mimic tap water: 0.1gNaCl x 1 mol/57.45g NaCl = .001741molNaCl

and since molarity is calcluated by mol/Liter....

600mL=.600L

.001741molNaCl/.6LH20 = .029 mol/L

Salt water: 2.5gNaCl x 1mol/57.45g NaCl = .0435molNaCl

.0435molNaCl/.1LH2O = .435mol/L

Therefore, different salt ratio creates the difference in molarity which proves different the salt concentration solutions. BOOM. 

Friday 9/6/13

http://theorganizedwife.wordpress.com/2012/01/30/organizing-with-the-number-three/

1. Our AP class has recently completed our first unit of the year (the first....of many). It included nomenclature, molecular and empirical formulas, percent composition, combustion analysis, and stoich. Labs were thrown at us left and right... but somehow we survived the fist weeks with the GPA KILLA. 

2. Personally, I've learned that a year without chemistry is a lot longer than I thought it would be, haha. I've also brushed up on my stoich skills and learned how to create my own procedures for the AP labs, which is definitely a lot harder than you'd think. Atom economy is also something I've learned about recently along with the guided lab's green chemistry. 

3. First off, I plan on NOT failing this upcoming test (which I was currently studying for). I also plan on learning chemistry more in depth as we move on from the review part of this AP class. I don't know if I should be excited or terrified honestly; but hey, bring it.