3.Phosphate-buffered saline (PBS) is a buffer solution commonlyused in biological research. Most formulations contain a mixture ofKCl and NaCl buffered to a pH of 7.40 using phosphate-containingcompounds.
a.The following reagents are available in your lab. Choose thecorrect reagents and calculate the volumes necessary to prepareexactly 5.0 L of a phosphate buffer with a pH of 7.40.
                                              0.100 M H3PO4 0.150 M Na2HPO4
                                               0.200M KH2PO4 0.120 M Na3PO4
b.Commercial PBS solutions are typically prepared by dissolvingsolid reagents in water and then adjusting the pH to 7.40 usingHCl. The formulation shown below is for the preparation of 10.0 Lof a PBS solution. What is the pH of this solution and how manymoles of HCl must be added to
adjust the pH to 7.40?
Component | Mass (g) |
NaCl | 80.0669 |
KCl | 2.0129 |
Na2HPO4 | 14.1960 |
KH2PO4 | 2.4496 |
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Question
1. When NO2 is bubbled into water, it is completely converted toHNO3 and HNO2 according to the reaction shown below. Calculate thepH and the molar concentrations of all dissolved species (H3O+,OH–, HNO2, HNO3, NO2–, and NO3–) in a solution prepared by bubbling4.601 g NO2 through 2.00 L of water.
2NO2(g) + H2O(l) → HNO3(aq) +HNO2(aq)
2. 12.6-g sample of Na2A (molar mass = 126 g/mol) isdissolved enough water to produce 1.00 L of solution. The pH ofthis solution is 9.85 and the equilibrium concentration of H2A is1.0 × 10–12 M. Determine the values of pKa1 andpKa2 for H2A
3.Phosphate-buffered saline (PBS) is a buffer solution commonlyused in biological research. Most formulations contain a mixture ofKCl and NaCl buffered to a pH of 7.40 using phosphate-containingcompounds.
a.The following reagents are available in your lab. Choose thecorrect reagents and calculate the volumes necessary to prepareexactly 5.0 L of a phosphate buffer with a pH of 7.40.
                                              0.100 M H3PO4 0.150 M Na2HPO4
                                               0.200M KH2PO4 0.120 M Na3PO4
b.Commercial PBS solutions are typically prepared by dissolvingsolid reagents in water and then adjusting the pH to 7.40 usingHCl. The formulation shown below is for the preparation of 10.0 Lof a PBS solution. What is the pH of this solution and how manymoles of HCl must be added to
adjust the pH to 7.40?
Component | Mass (g) |
NaCl | 80.0669 |
KCl | 2.0129 |
Na2HPO4 | 14.1960 |
KH2PO4 | 2.4496 |
4. Consider the potentiometric titration of 25.0 mL of 0.200 Mselenious acid (H2SeO3) with 0.250 M NaOH.
a. Identify the primary selenium-containing species present ateach point in the titration (A – E) shown below. Then sketch thetitration curve, identifying points A – E. Make sure toappropriately label the axes.
Point | NaOH Added (mL) | Se-Containing Species |
A | 0.00 |
B | 10.00 |
C | 20.00 |
D | 25.00 |
E | 40.00 |
