Notes

Reactions: (known + unknown)
CuSO4 + Ba(NO3)2 → Cu(NO3)2 (aq) + BaSO4 (s) Ba(NO3)2 (aq) + H2SO4 (aq)→ 2HNO3 + BaSO4 (s)
H2SO4 (aq) + 2KHCO3 (aq)→ 2CO2 (g) + 2H2O (l) + K2SO4 (aq) CuSO4 (aq) + 2NaOH (aq)→ Cu(OH)2 (s)+ Na2SO4 (aq)
2NaOH (aq) + NiCl2 (aq)→ Ni(OH)2 (s) + 2NaCl (aq)
KMnO4 (aq) + NaHSO3 (aq) + H2O (l)→ KOH (aq) + MnO2 (s) + 2 NaHSO4 (aq)
Solution letter
Technique #1 Technique #2
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A
C D
The pH of the solution was about 1, indicating that it is a strong acid.
The pH test indicated the solution being a strong base.
The solution has a distinct odor that no other solution gave.
Mixed it with solution G to form a precipitate since BaSO4 is not soluble.
Mixed it with solution B to form a precipitate since Cu(OH)2 is not soluble. The pH of the solution was about an 11, indicating that it is a strong base.
B
The observational color is blue, which indicates a transition metal is within the unknown and copper is known to be blue in solution.
During the flame test, it gave off a green color. When I looked up what element gives off a green color, the answer was Copper (II).
E
During the flame test, it gave off a purple color. When I looked up what element gives off a purple color, the answer was potassium.
Mixed it with solution A to form a gas since H2CO3 becomes CO2 and H2O.
F
During the flame test, it gave off a red color. When I looked up what element gives off a red color, the answer was Lithium.
The pH test indicated the solution being neutral, meaning that the amount of OH- and H+ created is equal.
G
During the flame test, it gave off a lime color. When I looked up what element gives off a lime color, the answer was Barium.
Mixed it with solution B to form a precipitate since BaSO4 is not soluble.
H
The observational color is green, which
indicates a transition metal is within the unknown and nickel is known to be green in solution.
Mixed it with solution C to form a precipitate since Ni(OH)2 is not soluble.
I
The observational color is dark purple, which indicates a transition metal is within the unknown and magnesium is known to be purple in solution.
Mixed it with solution M to form a precipitate.
J
The observational color is orange, which indicates a transition metal is within the unknown and iron is known to be orange in solution.
The pH of the solution was 1 and Fe (III) nitrate is known for its acidity.
K
The pH test indicated the solution being a neutral, meaning that the amount of OH- and H+ created is equal.
During the flame test, it gave off a yellow color. When I looked up what element gives off a yellow color, the answer was Sodium.
L
During the flame test, it gave off a slight purple color. When I looked up what element gives off a purple color, the answer was potassium.
The pH test indicated the solution being neutral, meaning that the amount of OH- and H+ created is equal.
M
Discussion:
Mixed it with solution M to form a precipitate.
After figuring all the previous solutions, it the last unknown not found as NaHSO3.
1. Answer the objective: How can we determine the identity of a group of unknown solutions using physical and chemical properties?
We can determine the identity of a group of unknown solutions by first using physical to eliminate some unknown solutions. The first one would be identifying the transition metal solutions. Any solution that has a color, whether blue or a dark purple, contains a transition metal. Next is odor and the only compound that has a distinctive odor is Ammonia. As for chemical properties, the pH test will indicate whether H+ or OH- is present and how
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concentrated it is. Another test that can be done for chemical properties is the flame test. During this, vibrant colors will appear which indicates that the solution is ionic. The last test that can be done for chemical properties are reactions between the knowns and unknowns. If certain solutions are mixed, a precipitate or gas will form.
2. How did you prove what the unknowns were?
See above ↑
Additional Discussion Questions:
1. How can you determine if a salt is acidic or basic?
It can be determined whether a salt is acidic or basic through putting it in solution and testing for its pH.
2. Explain why NaF is a basic salt?
NaF is a basic salt because if it is mixed with H2O, a weak acid would be made, HF, and a strong base is made, NaOH. The weak acid would cause the reaction to go reverse, and back again to create more NaOH.
3. State four methods to determine that a chemical reaction has taken place.
4 methods to determine that a chemical reaction has taken place are if a precipitate is formed, bubbling occurred, color change in the solution, and temperature change by either releasing (getting hotter) or absorbing heat (getting colder).
4. Which unknowns were the easiest to identify and why?
The unknowns that were the easiest to identify were any of the colored solutions, which includes B, H, I, and J, because I know that transitions metals will turn that solution in a distinct color. KMnO4 (I) was also easy to identify because I worked with it in a previous lab and know what it looks like. E, F, G, K and L were also relatively easy to identify because they gave off unique colors during the flame test. The only two that had to be distinguished after were E and L since they both had purple flames, which indicates potassium present.