A runner weighs 550 N and 71% of this weight is water. (a) How many moles of water are in the runner's body? (b) How many water molecules (H₂O) are there?

Two glass containers, of equal volume each hold a mole of gas. Container 1 is filled with hydrogen gas (molar mass 2 g / mol), and Container 2 holds helium (molar mass 4 g / mol). If the pressure of the gas in Container 1 equals the pressure of the gas in Container 2, which of the following is true?   (a)  The temperature of the gas in Container 1 is lower than the temperature of the gas in Container 2. (b)  The temperature of the gas in Container 1 is greater than the temperature of the gas in Container 2. (c)  The value of R for the gas in Container 1 is ½ the value of R for the gas in Container 2. (d)  The rms speed of the gas molecules in Container 1 is lower than the rms speed of the gas molecules in Container 2. (e)  The rms speed of the gas molecules in Container 1 is greater than the rms speed of the gas molecules in Container 2.

A cell doesn’t need a circulatory system, but your body does. Let’s do a quick calculation to see why. A typical cell has a diameter of 10 mm. The smallest mammals in the world, shrews, are about 10 μm across. Compute the diffusion time for oxygen molecules through water at 25°C for these two distances.

A spherical balloon of volume 4.07 x 10³ cm³ contains helium at a pressure of 1.21 x 105 Pa. How many moles of helium are in the balloon if the average kinetic energy of the helium atoms is 3.60 x 10-2² J? mol