During  a  field  trip,  an  instructor  touched  a  moth  resting  on  a  tree  trunk.  The  moth  raised  its  forewings  to  reveal large eyespots on its hind wings. The instructor asked why the moth lifted its wings. One student answered that sensory  receptors  had  fired  and  triggered  a  neuronal  reflex  culminating  in  the  contraction  of  certain  muscles.  A second student responded that the behaviour might frighten predators. Which statement best describes these explanations?

#Question id: 378

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following statements about buffers is true?

#Question id: 379

#Unit 1. Molecules and their Interaction Relevant to Biology

A compound has a pKa of 7.4. To 100 mL of a 1.0 M solution of this compound at pH 8.0 is added 30 mL of 1.0 M hydrochloric acid. The resulting solution is pH:

#Question id: 380

#Unit 1. Molecules and their Interaction Relevant to Biology

The Henderson-Hasselbalch equation:

#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:

#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?

#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

 Which of these statements is true of the resulting buffers?