biochem test 1
Calculate the pH of a 0.010 M solution of each of these compounds: a. Acetic acid b. Sodium acetatec. Ammoniad. Ammonium chloride
(a) 3.37; (b) 8.37; (c) 10.63; (d) 5.63.
What is the pH of 0.15 M HCl?
0.82.
What is the molar mass of nitrous oxide?
2(14) + 16 = 44 g/mol.
What is the pH of 0.10 M lactic acid (Ka = 1.3 × 10-4)?
2.44.
If a patient is given 20 g of nitrous oxide, how many molecules of nitrous oxide have been given? HINT: Use the molar mass to convert grams into moles, and then use Avogadro's number to convert moles into molecules.
20 g (1 mol/44 g) = 0.46 mole; 0.46 mol (6.02 × 1023 molecules/mol) = 2.7 × 1023 molecules.
What is the pH of a solution that is equal parts sodium lactate and lactic acid?
3.89.
What is the pKa of lactic acid?
3.89.
What is the molarity of pure water?
55.6 M.
What is the pH of a 0.10 M solution of sodium lactate?
8.44.
Naturally occurring bromine consists of two isotopes, 79Br and 81Br, in roughly equal amounts. What is the average atomic mass of bromine?
80 amu.
What is a buffer? How do you prepare a buffer?
A buffer is a solution that contains a weak acid and its conjugate base or a weak base and its conjugate acid. This system resists changes in pH.
What is the difference between physical and chemical changes?
A chemical change results in the formation of a new chemical substance. A physical change changes the state of a substance, but it is still the same substance.
What is the difference between a period and a group on the periodic table?
A period is a horizontal row that represents filling electron quantum energy levels. A group is a vertical column that contains elements with similar chemical and physical properties.
What is a solution? How does it differ from a colloid?
A solution is a homogeneous mixture that has one or more solutes dispersed at a molecular or ionic level throughout a medium called the solvent. The dispersed phase in a colloid is much larger than a typical molecule. For this reason, colloids exhibit the Tyndall effect, or the ability to trace out a ray of light shown through the colloid.
What is an acid? A base? A conjugate acid?
An acid is a species that donates a hydrogen ion (proton) to a base. When the base accepts the proton, it is converted into its conjugate acid.
What is an amphoteric species?
An amphoteric species can behave as either an acid or a base.
Define and describe molecules, atoms, compounds, mixtures.
An atom is the fundamental building block of all matter. Molecules are aggregates of atoms chemically bonded into a discrete unit. Compounds are comprised of two or more kinds of atoms. Mixtures are aggregates of two or more pure substances that can be separated through physical means.f
What is an ion? A cation? An anion? How do ions form?
An ion is an atom or group of atoms with a net electrical charge. Anions are negatively charged ions that are formed by addition of electrons. Cations are positively charged ions that are formed by the loss of electrons.
How does vapor pressure depend on temperature? On intermolecular forces?
As temperature increases, the vapor pressure increases. As intermolecular forces decrease, the vapor pressure increases.
List and describe the colligative properties of solutions.
As the concentration of solute particles increases, the vapor pressure de- creases, the boiling point increases, the freezing point decreases, and the osmotic pressure increases.
What geometry do you expect for an AX2E molecule, such as sulfur dioxde?
Bent.
Which has a higher boiling point, CHCl3 or CHI3? Why?
CHI3 (iodoform), because it contains the larger iodine atoms and, therefore, experiences more London forces.
What is the difference between an ionic bond and a covalent bond?
Covalent bonds result from the Columbic attraction for one or more shared pairs of electrons between two nuclei. Ionic bonds result from the Columbic attraction between oppositely charged ions.
Density is calculated from two extensive physical properties, namely mass and volume. Is density an intensive or an extensive physical property?
Density is intensive, even though it relates two extensive properties.
List and describe the three principle intermolecular forces.
Dipolar attractions result from the attraction between permanent molecular dipoles. Hydrogen bonding is a special type of dipolar interaction, but only occurs when a hydrogen atom is directly bonded to O, F, or N. London forces are temporary dipolar attractions that result from nonsymmetrical distribution of electrons in an atom or molecule.
How do you predict the charge of the ions derived from the representative elements?
For the representative metals, the cationic charge equals the group number. For representative nonmetals, the anionic charge equals the group number minus 8. Transition metals frequently form more than one cation.
Which conjugate acid-base pair is most important in buffering blood?
H PO - and HPO -2 244
Give the mass number, atomic number (Z), proton number (P), neutron number (N), and electron number (E) for the first four elements on the periodic table.
H: mass number = 1; Z = 1; P = 1; N = 0; E = 1; He: mass number = 4; Z = 2; P = 2; N = 2; E = 2; Li: mass number = 6; Z = 3; P = 3; N = 3; E = 3; Be: mass number = 9; Z = 4; P = 4; N = 5; E = 4.
Do you expect more ideal behavior from helium gas or water vapor, and why?
Helium gas, because water can form hydrogen bonds.
What's a hydrate?
Hydrates are compounds that absorb water into their crystalline structure. Formation of a hydrate is generally reversible.
What is the difference between intensive and extensive physical properties?
Intensive properties do not depend on sample size (e.g., density, color, etc.). Extensive physical properties depend on sample size (e.g., mass, volume, etc.).
Give one intensive physical property of water and one extensive physical property of water.
Intensive: density, colorless, ect.; extensive: mass, volume, etc.
How do you decide whether a compound is molecular or ionic?
Ionic compounds generally consist of a metal and one or more nonmetals, whereas molecular compounds contain only nonmetals.
What are isotopes?
Isotopes have the same atomic number but different neutron numbers.
What geometry do you expect for nitrous oxide? The atom connectivity is N-N-O.
Linear.
What is the difference between mass number and average atomic mass?
Mass number is equal to the proton number plus the neutron number. The average atomic mass appears on the periodic table and is the mass of each naturally occurring isotope of an element weighted by the fractional abundance of the isotope.
Classify and describe types of matter.
Matter can be either a pure substance or a mixture. Pure substances cannot be further broken down into simpler components through physical processes and can be either elements (one type of atom) or compounds (more than one type of atom). Mixtures can be homogeneous (aka. solutions) or heterogeneous. Heterogeneous mixtures exhibit phase boundaries, or sharp demarcations where the chemical and/or physical properties of the sample change. Mixtures are separable into pure substances through physical processes.
Is there a trend in the periodic table about which kind of ion an element is likely to form?
Metals (left side of the table) tend to form cations; nonmetals (right side of table) tend to form anions.
What is the difference between metals, nonmetals, and metalloids?
Metals are located on the left side of the periodic table. Metals tend to form cations, are generally ductile and malleable, and are good electrical and thermal conductors. Nonmetals are located on the right side of the periodic table. Nonmetals tend to form anions and have a wide variety of physical properties. Metalloids look like metals but have electrical conductivity intermediate between metals and nonmetals. For this reason, metalloids are called semiconductors.
What charge ion is sodium likely to form? How about a phosphide ion? How about a barium ion?
Na ; P ; Ba .
Is the pH of solutions containing these salts likely to be acidic, basic, or neutral? NaCl, NaI, NH4Cl, cocaine hydrochloride, sodium acetate, sodium palmitate.
NaCl (neutral), NaI (neutral), NH4Cl (acidic), cocaine hydrochloride (acid- ic), sodium acetate (basic), sodium palmitate (basic).
Do you expect nitrous oxide to be more soluble in the adipose (fatty, non- polar tissue) or in the blood? Explain.
Nitrous oxide has a small molecular dipole, but it is not very polar compared to water. Therefore, nitrous oxide is expected to be preferentially soluble in adipose tissue.
What is the conjugate base of hydroxide? Is it a stronger or weaker base than hydroxide?
O2- . It is a strong base.
Describe the organization of the periodic table (periods, groups, group number).
Periods are horizontal rows on the table. Each successive element has one additional proton and one additional electron. Each period represents fill- ing a quantum energy level on that series of atoms. Elements at the end of a period have filled electron energy shells and are especially stable. Groups are vertical columns. Members of the same group have similar chemical and physical properties. In the older A/B numbering system, representative elements have an A designation and the group number represents the number of valence electrons available for chemical reaction/bonding.
Give one physical property of water and one chemical property of water.
Physical: density is 1.0 g/mL; water is clear and colorless, etc. Chemical: water can be decomposed into 1 part oxygen and 2 parts hydrogen; water is the product of metabolizing food, etc.
If PV = nRT, what does R = ?
R = PV/nT
When acids and bases react, you normally get ___ and ___.
Salt and water.
Is glucose an ionic or molecular compound? The molecular formula of glu- cose is C6H12O6.
Since glucose contains only nonmetals, it is a molecular compound.
"Lactated ringers" contains sodium lactate. If the formula of sodium lactate is NaC3H5O3, what is the charge on the lactate ion? (lactate = C3H5O3 with some unspecified charge).
Since the Na+ ion has a +1 charge, the lactate ion must have a -1 charge, C3H5O3 -1.
If a mixture of nitrous and oxygen is bubbled through a spirometer having a large volume of water, which gas is more likely to be absorbed (dissolve in) the water? Explain.
Since the oxygen is less polar than the nitrous oxide, it is less likely to dissolve in water.
Rationalize the defining characteristics of the states of matter in terms of intermolecular forces and the kinetic molecular theory of matter.
Solids are characterized by definite volumes and shapes due to strong intermolecular forces that lock the molecules into a rigid crystalline lattice. Liquids are characterized a definite volume, but have no definite shape. Intermolecular attractions in liquids are sufficient to keep the molecules in contact (a condensed state of matter) but not strong enough to prevent the molecules from sliding around past each other. Thus, liquids have the ability to flow. Gases have neither a definite volume nor shape because there are negligible intermolecular forces between gas molecules.
List and describe the three states of matter.
Solids are characterized by definite volumes and shapes due to strong intermolecular forces that lock the molecules into a rigid crystalline lattice. Liquids are characterized by a definite volume, but have no definite shape. Intermolecular attractions in liquids are sufficient to keep the molecules in contact (a condensed state of matter) but not strong enough to prevent the molecules from sliding around past each other. Thus, liquids have the ability to flow. Gases have neither a definite volume nor shape because there are negligible intermolecular forces between gas molecules.
What is STP?
Standard temperature and pressure. T = 0°C and P = 1 bar = 100 kPa. Old- er texts set standard pressure as 1 atm, but this was revised by the IUPAC.
What is a surfactant? How do they break surface tension? Give examples of when this is useful.
Surface active agents, commonly known as soaps and detergents, have an ionic (or highly polar) hydrophilic end that allows the surfactant to interact with water molecules. The surfactant also has a hydrophobic tail that prevents the water molecules from interacting with each other. This reduces the surface tension and cohesion of the water. Cleaning and preventing the collapse of a premature baby's lungs are two applications of surfactants.
What is the standard molar volume of an ideal gas?
The SMV of an ideal gas is the volume occupied by one mole of gas at STP. Under the current definition of STP, the SMV = 22.7 L. The older definition of STP (273 K and 1 atm) gives an SMV of 22.4 L.
What is the pH scale?
The pH scale describes the level of acidity or alkalinity in a solution.
What are the representative elements? The transition elements?
The representative elements comprise the two "high rises" on either side of the periodic table. In the older numbering system, the representative elements belong to groups 1A through 8A. The transition elements comprise the center connection between the representative elements. In the A/B num- bering system, representative elements belong to the B groups.
How does a buffer prevent the pH from rising when a base is added?
The weak acid (HA) reacts with the added hydroxide ion to produce A-, thereby trading a strong base for a weak one.
If an anesthetic (like all other compounds) has a smaller molecular weight, it tends to have smaller intermolecular attractions. Therefore: a. A smaller anesthetic molecule will have a higher vapor pressure. b. A larger anesthetic molecule will have a higher vapor pressure. c. A smaller anesthetic molecule will have a higher boiling point. d. A larger anesthetic molecule has a greater tendency to evaporate.
These terms are relative between two specified solutions and have no mean- ing outside of a definite context. The hypertonic of two solutions has a higher solute particle concentration. Two solutions are isotonic if they have equal solute particle concentrations.
What role does the self-ionization of water play in acid-base chemistry?
This equilibrium fixes the ratio of the H+ and the OH- ions. This establishes the maximum and minimum acid strengths that can exist in water and es- tablishes 7.0 as the neutrality point.
You dissolve 90 g of sucrose (molar mass = 342 g/mol) in 1000 g of water. What is the molality of the solution? If the cryoscopic constant for water is 1.9 degrees/molal, what is the freezing point of the solution?
Two liquids are miscible if they are soluble in each other in all proportions.
Explain why water is a liquid at room temperature while carbon dioxide is a gas.
Water can form hydrogen bonds that can hold the water molecules into a liquid state even when the average kinetic energy of the molecules is relatively high.
Explain why NaCl dissolves in water but not in a nonpolar organic sol- vent.
When NaCl dissolves in water, is separates into Na+ ions and Cl- ions. These ions are surrounded by a poorly defined sphere of polar water molecules. Organic solvents are not sufficiently polar to solvate the ions and keep them away from each other, allowing them to settle back into the solid state.
Can a molecule be an element? Explain.
Yes. For example, oxygen is an element because it consists of only oxygen atoms. Oxygen gas is a molecule that consists of two atoms of oxygen chemically bound into an O2 molecule.
to be an effective buffer, the acid must:a. Have a pKa nearly equal to the desired pH b. Be a strong acid c. Have a strong conjugate base d. All of these.
a pKa nearly equal to the desired pH
Give examples of solutions that have: a. A liquid solute in a liquid solvent b. A solid solute in a liquid solvent c. A gaseous solute in a liquid solvent d. A solid solute in a solid solvent
a) Rubbing alcohol is 80% isopropanol and 20% water; (b) normal saline is 0.8% NaCl in water; (c) club soda has carbon dioxide dissolved in water; (d) an alloy is stainless steel.
What are the Lewis structures and geometries for CO2, H2O, CHCl3, CCl4, and SO2?
a)O C O(b)H O H(e)O S O
If the Ka of bicarbonate is 4.8 × 10-11, what is the pKa of bicarbonate? a. 10.30 b. 3.70 c. 7.00 d. 14.00
a. 10.30
Based on ions that the elements we discussed in class typically form, which of these is an UNlikely compound? a. Al3O2 b. BeO c. NaF d. FeS
a. Al3O2
All of these compounds are considered to be acids by chemists. Which is NOT a Brønsted acid? a. BF3 b. H3PO4 c. HCl d. All of these are Brønsted acids
a. BF3
Do you expect the equilibrium constant for binding carbon monoxide to hemoglobin (Hb) to be larger or smaller than the equilibrium constant for binding oxygen to hemoglobin? Explain. Hb + 4 CO = Hb(CO)4 Hb + 4 O2 = Hb(O2)4 a. Larger b. Smaller c. Nearly zero d. Nearly infinite
a. Larger
Blood cells placed into pure water will: a. Swell, because they are hypertonic to pure water. b. Shrink, because they are hypertonic to pure water. c. Swell, because they are hypotonic to pure water. d. Shrink, because they are hypotonic to pure water.
a. Swell, because they are hypertonic to pure water.
The reason specific gravity is often cited rather than density is that: a. Specific gravity has units that are consistent with the SI (metric) system. b. The numerical value of density depends on the mass and volume units chosen, whereas specific gravity is unit-independent. c. The specific gravity of bodily fluids is always close to 1. d. If the specific gravity of a substance is greater than 1, you know it will float on water.
b.
You have one liter of water. You add 1.0 × 10-8 moles of HCl, so now the molarity of the HCl is 1.0 × 10-8 M. What is the pH of the solution? Be careful! a. 8.00 b. 6.98 c. 7.00
b. 6.98
What is the conjugate base of bicarbonate, HCO -? 3 a. H CO - 23 b. CO 2- 3 c. OH-
b. CO 2- 3
Which of these concentration units shows temperature dependence? a. Molarity b. Molality c. Percent (w/v) d. Both A and C
b. Molality
Which of these is a chemical property of nitrous oxide gas, rather than a physical property? a. Nitrous oxide is less dense than oxygen gas. b. Nitrous oxide is flammable. c. Nitrous oxide is colorless. d. All of these are physical properties. e. All of these are chemical properties
b. Nitrous oxide is flammable.
Exactly 1 mole of NaCl is placed into 1 L of water. This mixture is then thoroughly mixed. a. The molarity of the solution will be equal to 1. b. The molarity of the solution will be less than 1. c. The molarity of the solution will be greater than 1. d. The molarity will equal the molality.
b. The molarity of the solution will be less than 1.
What is the hydrogen ion concentration in a solution whose pOH is 12.0? a. 2 M b. 1×10-12 M c. 1×10-2 M d. More information is needed.
c. 1×10-2 M
What is the pH of a 0.001 M solution of HCl? a. 1 b. 2 c. 3 d. 7
c. 3
Which of these lists only representative metals? a.Na, B, C, N, O b. C, Si, Ga, Sn c. Li, Na, K, Rb d. Fe, Co, Ni, Cu e. Ce, Pr, Ne, Pm
c. Li, Na, K, Rb
Surfactant therapy is used to prevent an infant's lungs from collapsing and "sticking together." Which of these is the most reasonable rationale for this effect? a. The surfactant establishes a favorable osmotic potential between the lung tissues. b. The surfactant cleans the surface of the lungs. c. Surfactants reduce both surface tension and adhesive forces in water. d. The surfactant lowers the freezing point of the aqueous portion of the lung tissue.
c. Surfactants reduce both surface tension and adhesive forces in water.
What is the conjugate ACID of nitric acid (HNO3)? a. H+ b. H3O+ c. HNO2 d. H NO
d. H NO
How is density different from specific gravity?
density is unit dependent and equal to the mass of the substance divided by the volume of the substance. The value of the density, therefore, depends on the units of the mass and the volume. Specific gravity is equal to the density of the substance divided by the density of water (in the same units) and is, therefore, a constant numerical value.
Which of these is a common property of metals? a. Ductility b. Good electrical conductivity c. Tendency to form cations d. Shiny and lustrous surface e. All of the above
e. All of the above
Which of these statements is true of the elements symbolized by 14/6X and 14/7Y? 7 a. X and Y are isotopes of each other. b. X and Y are in the same chemical family. c. Y has more neutrons but fewer protons that X. d. X and Y have the same atomic number. e. None of these statements is correct.
e. None of these statements is correct.
What is an equilibrium constant, and what does its size indicate?
in a dynamic equilibrium, the population of two or more states is free to move between states. However, the ratio of the populations of each state is a constant value.
Which colligative property has the most profound impact on physical properties?
osmotic pressure.
what is the pH of vomit, if the H+ concentration is 0.1 moles/L?
pH = 1.
if blood pH is 7.30, what is the concentration of the H+ ion, the OH- ion, and the pOH?
pOH = 6.70; [H+] = 5.0 × 10-8 M; [OH-] = 2.0 × 10-7 M.
How does temperature normally affect solubility of solid solutes? Gaseous solutes?
this depends on the relative magnitudes of the solvation energy and the lattice energy of the species. As the magnitude of the solvation energy increases, the heat of solution becomes more exothermic. As the magnitude of the lattice energy increases, the heat of solution becomes more endothermic.
