Biology: Life on Earth
10th Edition
ISBN: 9780321729712
Author: Gerald Audesirk, Teresa Audesirk, Bruce E. Byers
Publisher: Benjamin Cummings
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Textbook Question
Chapter 2, Problem 8RQ
Define pH scale, acid, base, and buffer. How do buffers reduce changes in pH when hydrogen ions or hydroxide ions are added to a solution? Why is this phenomenon important in organisms?
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What important role do buffers play in organisms? What prevents a strong acid or strong base from working as a buffer?
pH expresses the molar concentration of hydronium ions in an
aqueous solution on a logarithmic scale. (Note that it is
common to use the hydrogen ion, H*, to represent the
hydronium ion, H3O+.)
pH = -log[H3O+]
[H3O+] = 10-PH
As pH decreases, acidity increases. As pH increases, acidity
decreases.
• Acidic solution: pH 7
Part A - Calculating pH
Submit
[H₂0+] 1
Acidic
pH 01
10¹ 102 103 104 105 106 107 108 109 10-10 10-11 10-12 10-13 10-14
stomach
acid
3
wine
lemon tomatoes
juice
vinegar,
black
soft drinks, coffee
beer
6
Neutral
urine
milk
7
human
blood
pure
water
sea-
water
baking
soda
10 11 12 13 14
milk
of
magnesia house-
hold
ammonia
oven
cleaner
Basic
household
bleach
Adapted from Biological Science by Freeman ©2008 Pearson Education, Inc.
What is the pH of an aqueous solution with the hydronium ion concentration
[H3O+] = 2 x 10-14 M?
Make sure that your answer has the correct number of significant figures. For help determining the correct number of significant figures, see Hint 3.
►…
Match each weak acid with the pH value at which it would buffer.
pH 3
ammonium (PK, of 9.25)
chloroacetic acid (pK, of 2.87)
acetic acid (pK₂ of 4.76)
formic acid (PK, of 3.8)
pH 5
Answer Bank
boric acid (PK, of 9.24)
pH 9
hydrazoic acid (PK, of 4.6)
Chapter 2 Solutions
Biology: Life on Earth
Ch. 2 - Fill-in-the-Blank An atom consists of an atomic...Ch. 2 - Fill-in-the-Blank An atom that has lost or gained...Ch. 2 - Fill-in-the-Blank Atoms of the same element that...Ch. 2 - An atom with an outermost electron shell that is...Ch. 2 - Water is described as _____ because each water...Ch. 2 - Based on Table 2–1 how many neutrons are there in...Ch. 2 - Distinguish between atoms and molecules; between...Ch. 2 - Define isotopes and describe the properties of...Ch. 2 - 3. Compare and contrast covalent bonds and ionic...Ch. 2 - 4. Explain how polar covalent bonds allow hydrogen...
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- if pH level of solution changes from pH 5 to pH 2, how much acidity increased in that solution and why?arrow_forwardI want to make a buffer solution containing 1 M glycene pH = 10 (Na+), 1 mM ZnCl2 , 1 mM MgCl2. I have the stock solutions 1 M glycene, 1 M MgCl2, 1 M ZnCl2, and 10 M NaOH. My final volume of buffer solution needs to be 250ml. how much (in ml) of each solution should i put into my buffer?arrow_forwardWhy are buffers important in living systems? please explainarrow_forward
- Which of the following is TRUE if pH is higher than the pka of the buffer? O [weak acid] approximately 0 O [conjugate base] = [weak acid] [conjugate base] > [weak acid] O [conjugate base] < [weak acid]arrow_forwardA solution has a hydrogen ion concentration of 0.01 mol/L. What is its pH? What is its hydroxide ion concentration? Is it acidic, basic, or neutral? How does the hydrogen ion concentration of this solution differ from one with a pH of 1?arrow_forwardWhich of the following combinations would be the best choice to buffer the pH of a solution at approximately 7? Ionization Constants for Aqueous Weak Acids at 25 °C Acid K. (pK,) Conjugate Base Hydrogen phthalate ion, Cg H4(CO2H)(CO2) Acetic acid, CH3 CO,H Acetate ion, CH; CO2- 1.8 x 10-5 (4.74) Weak Acid Phthalic acid, C6 H4 (CO,H)2 1.3 x 10-3 (2.89) Dihydrogen phosphate Hydrogen phosphate ion, H2 PO4 Hydrogen phosphate ion, HPO42 6.2 x 10-8 (7.21) ion, HPO,2- Phosphate ion, PO,* 3.6 x 10-13 (12.44) O Na, HPO4 and NagPO4 O NaH2 PO4 and NazHPO4 O H;PO4 and NaH2 PO4arrow_forward
- You need to prepare 500 ml PBS buffer, a solution commonly used in biological research. The buffer helps to maintain the pH, and the osmolarity, as well as ion concentrations of PBS buffer, match those of the human body. PBS buffer consists of the following components: 137 mM NaCl, 2.7 mM KCl, 10 mM Na2HPO4, 1.8 mM KH2PO4. How would you prepare the buffer?arrow_forwardfor 0.9% NaCl solution and 10% NaCl solution, which one has higher concentration of WATER?arrow_forwardWhich of the following buffers has the highest buffering capacity? 0.15 M phosphate buffer at pH 7.2 0.015 M phosphate buffer at pH 7.2 0.01 M phosphate buffer at pH 7.2 0.10 M phosphate buffer at pH 7.2arrow_forward
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