Question

multiple choice 1 point
which of the following statements is correct regarding net diffusion?
the rate is independent of temperature.
molecular weight of a substance does not affect the rate.
the greater the concentration gradient, the faster the rate.
the lower the temperature, the faster the rate.
42
multiple choice 1 point
a red blood cell placed in pure water would _.
neither shrink nor swell
swell initially, then shrink as equilibrium is reached
swell and burst
shrink

Explanation:

Question 41

Step1: Analyze each option

• Option 1: Net - diffusion rate is temperature - dependent. Higher temperature increases molecular kinetic energy, so this option is wrong.
• Option 2: Molecular weight affects diffusion rate (e.g., Graham's law). Lighter molecules diffuse faster, so this option is wrong.
• Option 3: According to Fick's law of diffusion ($J=-D\frac{dC}{dx}$, where $J$ is the diffusion flux, $D$ is the diffusion coefficient, and $\frac{dC}{dx}$ is the concentration gradient), a greater concentration gradient ($\frac{dC}{dx}$) leads to a higher diffusion rate. This option is correct.
• Option 4: Lower temperature slows down molecular motion, reducing the diffusion rate. So this option is wrong.

Question 42

Step1: Understand osmosis

Pure water is hypotonic compared to the interior of a red - blood cell (which has a higher solute concentration). Water will move into the red - blood cell by osmosis.

Step2: Consider cell structure

Red - blood cells have no cell wall. As water enters, the cell swells. Since there is no rigid structure to stop the expansion, the cell will swell and burst.

Answer:

Question 41: The greater the concentration gradient, the faster the rate.
Question 42: swell and burst