He then went and showed us a video on the Chemistry website, found here. It corresponds with question 5 on page 12. In the video, the first substance that was dissolved in the water was NaCl, sodium chloride. Mr. H explained that the "Mickey Mouses" (H2O) were connecting with sodium chloride. The positive of H2O, H, forms a bond with the negative Cl ion. Then, the O, the negative ion in H2O, bonds with the positive Na. This is an example of dissociated ions.
That is why the light bulb lighted in the video; it is an example of a strong electrolyte. He then explained the next two examples. The second example is called a weak electrolyte because there are more associated ions (ions that did not break off and make bonds with the water) than dissociated ions. This causes the light bulb to light very dimly. When methanol is added to the water, it does not dissociate into ions. This is called a nonelectrolyte.
For Question 6, we had to decide what type of electrolyte it was by the picture. The first picture is SE, strong electrolyte. Someone in the class explained that since there were no bonds and just molecules in the picture, it means that it completely dissociated and therefore is a strong electrolyte. The second picture is a non-electrolyte because there are no floating ions that are separated. Finally, the last one, you guessed it, is weak electrolyte. This is because there are some associated bonds, but there are other dissociated ions, too.
We moved onto question 7, now. We had to find the major species that would be in water by the compound given. He went through A, B, C, D, and F together with us. The answers are as follows:
A.) Compound: NH4Cl
Major Species: NH4+, Cl-, H2O
B.) Compound: C2H5OH
Major Species: C2H5OH, H2O
C.) Compound: H2SO4
Major Species: H+, SO4 2-, H2O
D.) Compound: NaC2H3O2
Major Species: Na+, C2H3O2, H2O
F.) Compound: HF
Major Species: HF, H2O
Minor Species: H+, F-
Note:
- All soluble ionic solids are strong electrolytes.
- Certain acids are strong electrolytes and goes as follows: HCl, HNO3, H2SO4, HBr, HI and HClO4
- Other acids are referred to as weak electrolytes.
- Molecular compounds held together by covalent bonds do NOT dissociate and are considered non-electrolytes.
PAGE 13
For 1a and 1b, refer to Hannah's blog on how to do them. For C and D, the steps are as follows to solve:
- Get the formula of reactants
- Write formula of product AND charges
- The state that it is in (solid, gas, liquid, or aqueous)
- Balance
LAB FROM YESTERDAY/PAGE 13
Mr. H made us take out our little data sheets from the lab, Chemical Drop Outs. He explained that each row (horizontal) had sodium (Na) and the columns (vertical) had nitrates (NO3). We had page 13 out, to refer to the box on the top. It has the solubility rules. For the rows, focus on the ANION, not cation (Na). Similarly, focus on the CATION, not anion (NO3). Mr. H had an example on the board, but he said that most carbonates are insoluble. Insoluble, meaning that there are more PPT's written in the boxes in the row/column. For the lab Conclusion/discussion, we had to write a sentence about each row and column. For example, for the row of Na2CO3, most of my group's boxes are written with PPT. So, this means that carbonate is insoluble. So, my sentence for that row would be carbonate is insoluble with exceptions of aluminum, ammonium, and calcium. The EXCEPT is there because not all of the reactants had a precipitate. Those would be the NR in the boxes. If a row or column has more NR's than PPT's, you would write that that row/column is soluble with exceptions of the boxes with PPT in it. Every group is different, which would result in different sentences.
Remember that the homework for tonight is a WebAssign and a Delicious bookmark!
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