Buffers PRE-LABORATORY ASSIGNMENT To be completed before attending lab: 1. Ident

Question

Buffers PRE-LABORATORY ASSIGNMENT To be completed before attending lab: 1. Identify all potentially hazardous steps in your procedure. In your own words, explain what safety precautions should be taken and why? 2. Define the following: acid, conjugate acid, base, conjugate base, pH, pK., and buffer strength. 3. Starting with the K, equation, derive the Henderson-Hasselbach equation. 4. Use the Henderson-Hasselbalch equation to perform the following calculations. The K, of acetic acid is 1.8 x 10°. Review your calculations with your instructor before preparing the buffer solutions. Buffer A: Calculate the mass of solid sodium acetate required to mix with 100.0 mL of 0.1 Macetic acid to prepare a pH 4 buffer. Record the mass in your data table. Buffer B: Calculate the mass of solid sodium acetate required to mix with 100.0 mL of 1.0M acetic acid to prepare a pH 4 buffer. Record the mass in your data table. 5. A weak acid (HA) has a pk, -2.77. Assuming that the volumes are additive, calculate the volume (in mL) of 0.500 MHA, 0.500 M NaA, and water required to make 250.00 mL of a buffer with a total concentration of 0.400 M and (a) pH-2.77: (b) pH-2.25; (c) pH-3.00. 6. Calculate the buffer strength of the three buffers in the previous problem. WHAT TO DISCUSS IN YOUR CONCLUSION

Explanation / Answer

1)

Potentially hazardous steps can be:

1.Overusage of chemical

2.Improper conditions of experiment

3.Spillage

4. Ignorance of the sequence of steps

Safety precautions:

Each of the forms of radiation has sufficient energy to break chemical bonds

and damage human tissue. Potential harm is proportional to the energy

absorbed which in turn is affected by the amount of exposure.

Ionizing radiations:

alpha particles

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