## Additional Problems

1. A sample of acidic precipitation is found to have a pH of 4.2. Upon analysis it is found to have a total sulfur concentration of 0.000010 M. Calculate the concentration of nitric acid in the sample, and from the ratio of nitric to total acid decide whether the air sample probably originated in eastern or in western North America.

2. If the pH of rainfall in upstate New York is found to be 4-0, and if the acidity is half due to nitric acid and half to the two hydrogen ions released by sulfuric acid, calculate the masses of the primary pollutants nitric oxide and sulfur dioxide that are required to acidify one liter of such rain.

3. The pH in a lake of size 3.0 km X 8.0 km and an average depth of 100 m is found to be 4.5. Calculate the mass of calcium carbonate that must be added to the lake water in order to raise its pH to 6.0.

4. The pH of a sample of rain is found to be 4.0. Calculate the percentage of HS04 that is ionized in this sample, given that the acid dissociation constant for the second stage of ionization of H2S04 is 1.2 X 10mol URepeat the calculation for a pH of 3.0. Is the trend shown by these calculations consistent with qualitative predictions made according to Le Chatelier's principle (which states that the position of equilibrium shifts so as to minimize the effect of any stress) J [Hint: Write the expression for the acid dissociation constant for the weak acid in terms of the concentrations of the reac-tones and products, and use the stoichiometry of the balanced equation to reduce the number of unknowns to one,]

5. Calculate the mass of fine particles inhaled by an adult each year, assuming he/she inhales about 350 L of air per hour and that the average PM2 5 index of this air is 10 /u,g/m3. Assuming that each particle has a diameter of about 1 fim and that the density of the particles is about 0.5 g/mL, calculate the total surface area of this annual load of particles. [Hint: The surface area of a spherical particle is equal to 4ttt2, where r is its radius.]

6. The detection threshold of formaldehyde by humans is about 100 ppb. Would a typical human be able to detect formaldehyde at a concentration of 250 ¿ig/m3 if the air temperature was 23°C and the pressure 1.00 atm?

7. What mass of formaldehyde gas must be released from building materials, carpets, etc.

in order to produce a concentration of 0.50 pptn of the gas in a room having dimensions of 4mX5mX2m?

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