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TLS Online TPP Program

#Question id: 13210

In Cohesion–Tension Theory, the pressure gradients needed to move water through the xylem could result from

#Unit 6. System Physiology – Plant
  1. the generation of positive pressures at the base of the plant or negative pressures at the top of the plant
  2. the generation of positive pressure both at the base of the plant and at the top of the plant
  3. the generation of negative pressure both at the base of the plant and at the top of the plant 
  4. the generation of negative pressure at the base of the plant or positive pressure at the top of the plant   
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TLS Online TPP Program

#Question id: 380

#Unit 1. Molecules and their Interaction Relevant to Biology

The Henderson-Hasselbalch equation:
TLS Online TPP Program

#Question id: 381

#Unit 1. Molecules and their Interaction Relevant to Biology

Consider an acetate buffer, initially at the same pH as its pKa (4.76). When sodium hydroxide (NaOH) is mixed with this buffer, the:
TLS Online TPP Program

#Question id: 382

#Unit 1. Molecules and their Interaction Relevant to Biology

The molar ratio of sodium acetate to acetic acid in a buffer solution with a pH OF 5.76 is 10:1. Assuming the total buffer concentration is 2.2 X 10-2 mol/L, how many grams of sodium acetate (m.w. 82) and how many grams of acetic acid (m.w. 60) should be used in preparing a litre of the solution?
TLS Online TPP Program

#Question id: 383

#Unit 1. Molecules and their Interaction Relevant to Biology

Three buffers are made by combining a 1 M solution of acetic acid with a 1 M solution of sodium acetate in the ratios shown below

1 M acetic acid              

1 M sodium acetate  

Buffer 1: 10 mL

 90 mL

Buffer 2: 50 mL

50 mL

Buffer 3: 90 mL

10 mL

 Which of these statements is true of the resulting buffers?
TLS Online TPP Program

#Question id: 384

#Unit 1. Molecules and their Interaction Relevant to Biology

A solution was prepared by dissolving 0.02 moles of acetic acid (HOAc; pKa = 4.8) in water to give 1 liter of solution. What is the pH? To this solution was then added 0.008 moles of concentrated sodium hydroxide (NaOH). What is the new pH? (In this problem, you may ignore changes in volume due to the addition of NaOH).
TLS Online TPP Program

#Question id: 386

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following properties of water does not contribute to the fitness of the aqueous environment for living organisms?