Acidic and Basic Anhydrides

14-1 Acidic and Basic Anhydrides LAB

When dissolved in water, the oxide of a metal fo= rms a basic solution. The oxide of a nonmetal when dissolved in water forms an ac= idic solution. Unless water is added to them, the oxides of both metals and nonm= etals are anhydrides, that is, compounds without water. Because a metallic oxide = in water forms a basic solution, a metallic oxide is called a basic anhydride.= The purpose of this activity is to form acidic and basic solutions by using an acidic anhydride and a basic anhydride.

OBJECTIVES

• Prepare a basic solution using a basic anhydride.

• Prepare an acidic solution using an acidic anhydride.

• React<= /span> the= acidic and basic solutions to form a salt.

HYPOTHESIS:

MATERIALS

thin-stem pipet=

tap water

gas generating microplate

toothpick

marble chips

chemical scoop

PROCEDURE

1. Form a hypothesis about whether the solut= ions formed by dissolving calcium oxide in tap water and a carbon oxide in tap w= ater will be acidic or basic.

= 2. Place a small piece of marble (CaCO₃)= in well A.

3. Using a clean microtip pipet, place 1⁄2-pipet of tap water in wells B, D, and F of the gas generato= r microplate.

= 4. Add 2 drops of universal indicator to wells B, D= , and F. Note the color of the universal indicator and the approximate pH in your Data and Observations.

5. Place 25 drops of HCl= in well A of the microplate.

CAUTION: HCl is corrosive. It burns skin and clothing.

6. Cove= r well A with black top with small tube.

7. Direct the tube into well B.

8. Allow the gas produced to bubble through well B. Note the color of= the universal indicator-water solution in your Data and Observations.

9. Using a chemical scoop, place a few crystals of = calcium oxide into well D. Note the color of the universal indicator-water solution= in your Data and Observations.

10. Allow the solid to settle out in well D. Using a= clean microtip pipet, rem= ove approximately 1⁄8-pipet of the liquid from well D.<= /p>

11. Place 10 drops of liquid from well D into well H= .

12. Using a clean microtip pipet, remove approximately 1⁄8-pipet of liquid= from well B. Place 10 drops of the liquid from well B into well H.

13. Mix the liquid in H thoroughly with a toothpick.= Note the color of the universal indicator-water solution in your Data and Observations.

DATA AND OBSERVATIONS

1. What color was the universal indicator in tap wa= ter (B, D, F) alone?

2. What was the color of the universal indicator wh= en the gas was bubbled through the water in well B?

3. What was the color of the universal indicator wh= en calcium oxide was added to the water in well D?

4. What happened to the universal indicator when th= e two solutions were mixed in well H?

ANALYSIS

1. Balance this equation, which describes the react= ion in well A containing the marble chip and HCl.=

_____ CaCO₃ + _____ HCl à _____ CO2 + _____ H₂₌O + _____ CaCl2

2. Balance this equation, which describes what happ= ened to the water in well B.

_____ CO₂ + _____ H₂O à _____ H2CO₃

3. Balance this equation, which describes what happ= ened when calcium oxide was added to the water in well D.

_____ CaO + _____ H₂₌O à _____ Ca(OH)₂

4. Balance this equation, which describes the react= ion in well H.

_____ Ca(OH)₂+ _____ H₂₌CO₃ à _____ CaCO₃ + _____ H₂O

CONCLUSIONS

1. Is CO₂ an acidic or a basic anhydride= ?

2. Is CaO an acidic or = a basic anhydride?

3. a. Is the product of the chemicals from well B acid= ic, basic, or neutral?

b. Explain your answer.

4. a. Is the product of the chemicals from well D acid= ic, basic, or neutral?

b. Explain your answer.

EXTENSION AND APPLICATION

1. When a salt is dissolved in water, the salt solu= tion almost never has a neutral pH. Why?

2. How might the pH of a solution be changed by a s= alt?