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a Safari all令 4:15 PM * 19% Laboratory Experiments 267 standardize knob until the pH meter indicates the exact pH of the buffer solution. Wait 5 s to be certain that the reading remains constant. Once you have standardized the pH meter, do not readjust the standardize knob. Turn the function knob to standby. Carefully lift the electrodes from the buffer and rinse them with distilled water. The pH meter is now ready to use to measure pH. 2. Effect of Acid and Base on the Buffer pH Pour half (32 mL) of the buffer solution you prepared above into another 150-mL beaker. Label the two beakers 1 and 2. (CAUTION: Concentrated HCL can cause severe burns. Avoid contact with it. If you come in contact with it, immediately wash the area with copious amounts of water.) Pipet 1.0 mL of 6.0 M HCl into beaker 1, mix, and then measure the pH of the re- sultant solution and record the pH. Remember to rinse the electrodes be- tween pH measurements. (CAUTION: Sodium hydroxide can cause severe burns. Avoid contact with it. If you come in contact with it, immediately wash the area with copious amounts of water.) Similarly, pipet 1.0 mL of 6.0 MNaOH into beaker 2, mix, and then measure and record the pH of the resultant solution. Calculate the pH values of the original buffer solution, the values after the additions of the HCl and NaOH. How do the measured and calculated values compare? Dispose of the chemicals in the designated receptacles. Before beginning this experiment in the laboratory, you should be able toan swer the following questions: PRE LAB QUESTIONS 1. Define Brønsted-Lowry acids and bases. 2. Which of the following ions will react with water in a hydrolysis reac- tion: Nat, Ca2+, Cu2+,Zn2*,F, So,Br? For those ions in question 2 that undergo hydrolysis, write net ionic equations for the hydrolysis reaction. The Ka for HCN is 4.9 à 10-10 What is the value of Kb for CN-? 3. 4. 5. What are the conjugate base and conjugate acid of H2PO4? 6. From what acid and what base were the following salts made: CaSO4, NH Br, and BaCl2? 7. Define the term salt Tell whether 0.1 M solutions of the following salts would be acidic, neutral, or basic: BaCl2, CuSO4, (NH4) S04, ZnCl2, NaCN. If the pH of a solution is 8, what are the hydrogen- and hydroxide-ion 8. 9. concentrations? The pH of a 0.1 M MCI (M* is an unknown cation) was found to be 4.7 Write a net ionic equation for the hydrolysis of M and its correspond ing equilibrium expression Kp. Calculate the value of Kp What is the pH of a solution that is 0.10 M HC2H302 and 0.20 M NaC2H3O2? Ka for acetic acid 1.8 à 10-b 10. 11.
a Safari all令 4:15 PM * 19% Laboratory Experiments 267 standardize knob until the pH meter indicates the exact pH of the buffer solution. Wait 5 s to be certain that the reading remains constant. Once you have standardized the pH meter, do not readjust the standardize knob. Turn the function knob to standby. Carefully lift the electrodes from the buffer and rinse them with distilled water. The pH meter is now ready to use to measure pH. 2. Effect of Acid and Base on the Buffer pH Pour half (32 mL) of the buffer solution you prepared above into another 150-mL beaker. Label the two beakers 1 and 2. (CAUTION: Concentrated HCL can cause severe burns. Avoid contact with it. If you come in contact with it, immediately wash the area with copious amounts of water.) Pipet 1.0 mL of 6.0 M HCl into beaker 1, mix, and then measure the pH of the re- sultant solution and record the pH. Remember to rinse the electrodes be- tween pH measurements. (CAUTION: Sodium hydroxide can cause severe burns. Avoid contact with it. If you come in contact with it, immediately wash the area with copious amounts of water.) Similarly, pipet 1.0 mL of 6.0 MNaOH into beaker 2, mix, and then measure and record the pH of the resultant solution. Calculate the pH values of the original buffer solution, the values after the additions of the HCl and NaOH. How do the measured and calculated values compare? Dispose of the chemicals in the designated receptacles. Before beginning this experiment in the laboratory, you should be able toan swer the following questions: PRE LAB QUESTIONS 1. Define Brønsted-Lowry acids and bases. 2. Which of the following ions will react with water in a hydrolysis reac- tion: Nat, Ca2+, Cu2+,Zn2*,F, So,Br? For those ions in question 2 that undergo hydrolysis, write net ionic equations for the hydrolysis reaction. The Ka for HCN is 4.9 à 10-10 What is the value of Kb for CN-? 3. 4. 5. What are the conjugate base and conjugate acid of H2PO4? 6. From what acid and what base were the following salts made: CaSO4, NH Br, and BaCl2? 7. Define the term salt Tell whether 0.1 M solutions of the following salts would be acidic, neutral, or basic: BaCl2, CuSO4, (NH4) S04, ZnCl2, NaCN. If the pH of a solution is 8, what are the hydrogen- and hydroxide-ion 8. 9. concentrations? The pH of a 0.1 M MCI (M* is an unknown cation) was found to be 4.7 Write a net ionic equation for the hydrolysis of M and its correspond ing equilibrium expression Kp. Calculate the value of Kp What is the pH of a solution that is 0.10 M HC2H302 and 0.20 M NaC2H3O2? Ka for acetic acid 1.8 à 10-b 10. 11.
Collen VonLv2
15 Feb 2019