Buffers_tkl_mcd_KEY_F08 - Chem 1A Fall 2007 Challenge...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Chem 1A Fall 2007 10/10-16/07 Challenge Problem - Buffers 20 mL of 0.10M weak acid is titrated with 0.10M NaOH 20 mL of 0.20M strong acid is titrated with 0.10M NaOH 20 mL of 0.10M H 2 CO 3 (pKa1= 6.35, pKa2= 10.3) is titrated with 0.10M NaOH p H p H p H Volume of Titrant Volume of Titrant Volume of Titrant 20 mL of 0.10M HCl is titrated with 0.05M NaOH 20 mL of 0.20M strong base is titrated with 0.10M HCl 20 mL of 0.10M weak base is titrated with 0.10M HCl p H p H p H Volume of Titrant Volume of Titrant Volume of Titrant × × × × × × ×
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chem 1A Fall 2007 10/10-16/07 Challenge Problem - Buffers 1) In order to make carbonated water, soda makers dissolve carbon dioxide gas, CO 2 (g), into water in the following reaction: CO 2 (g) CO 2 (aq) a) Write the equilibrium expression (Henry’s Law constant), K H, for the reaction. 2 )] ( [ 2 CO H P aq CO K = b) How does K H vary with increasing temperature? Use the evidence in Figure 1 to justify your response. K H decreases as temperature increases. At higher temperatures, if comparing the same pressure (the denominator), the solubility of CO 2 (the numerator) is smaller for higher temperatures. 2) Using the data in Figure 1, which of the following conditions would be most optimal for making carbonated water? High Pressure Low Pressure High Temperature Low Temperature Justify your answer using Le Chatelier’s principle. Increasing the pressure of the gas (P CO2 ) drives the chemical equation towards creating more products, dissolved CO 2 , to sustain the equilibrium ratio, K H . According to Figure 1, decreasing temperature at constant pressure, results in increased dissolved CO 2 , so decreasing the temperature (or removing heat) must increase the K H , which drives equilibrium to favoring more products. 3) Kristine and Karen are arguing about the best conditions for making soda water. Who do you agree with? Explain your reasoning. Kristine: We’ll get more CO 2 dissolved in water if we increase the air pressure above the water to 5 atm. Karen: We’ll get more CO 2 dissolved in water if we put 0.5 atm of CO 2 gas in a vacuum chamber above the water. Figure 1: Solubility of CO 2 (aq) in water vs. Pressure of CO 2 (g)
Background image of page 2
Chem 1A Fall 2007 10/10-16/07 Challenge Problem - Buffers **NOTE to GSI’s: The composition of air has been intentionally left out to see if students recognize the need for knowing the difference between partial and total pressure. When students ask, here is the composition of air: N 2 78.084% O 2 20.947% Ar 0.934% CO 2 0.033% I’d agree with Karen. The percent of CO 2 (g) in air is only around 0.033% so even though the total pressure in Karen’s scenario is less than the total pressure in Kristine’s scenario, the partial pressure of CO 2 (g) in Karen’s scenario is greater than the partial pressure of CO 2 (g) in Kristine’s scenario. 4)
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 9

Buffers_tkl_mcd_KEY_F08 - Chem 1A Fall 2007 Challenge...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online