Unit 1: Questions
How many electrons does an atom of sulfur have in its valence shell? A) 6 B) 16 C) 8 D) 4 E) 32
A)
Which of these individuals is likely to be most successful in an evolutionary sense? A) an organism that dies after five days of life but leaves 10 offspring, all of whom survive to reproduce B) an organism that lives 100 years and leaves two offspring, both of whom survive to reproduce C) a reproductively sterile individual who never falls ill D) a male who mates with 20 females and fathers one offspring E) a female who mates with 20 males and produces one offspring that lives to reproduce
A)
When two atoms are equally electronegative, they will interact to form A) polar covalent bonds B) ionic bonds C) hydrogen bonds D) non polar covalent bonds E) van der Waals interactions
D)
What chemical change occurs to ATP when it reacts with water and releases energy?
The ATP molecule loses a phosphate, becoming ADP
What does the term amino acid signify about the structure of such a molecule?
An amino acid has both an amino group (-NH2), which makes it an amine, and a carboxyl group (-COOH) which makes It a carboxylic acid
An atom has 6 electrons in its outer shell. How many unpaired electrons does it have? A) 0 B) 2 C) 2 or 4 D) 4 E) 6
B)
In what way are elements in the same column of the periodic table the same? A) they have the same number of protons B) they have the same number of electrons in their valence shell C) They have the same number of neutrons D) they have the same number of electron shells E) they have the same number of electrons
B)
What is the maximum number of covalent bonds an element with atomic number 8 can make with hydrogen? A) 1 B) 2 C) 3 D) 4 E) 6
B)
Van der Waals interactions result when A) electrons are not symmetrically distributed in a molecule B) molecules held by ionic bonds react with water C) two polar covalent bonds react D) hybrid orbitals overlap E) a hydrogen atom loses an electron
A)
What is the pH of a solution with a hydroxyl ion [OH-] concentration of 10-12 M? A) 10-8 M B) 0.01 M C) 10-6 M D) 8 M E) 8 x 10-6 M
A)
In a high school laboratory, which of the following constitutes an experiment? I. learning to use a microscope by examining fixed specimens on slides
A) (I, II, and IV are preparation or examining; no actual experiment is being done opposed to III)
Which type of chemical reaction, if any, occurs faster at equilibrium: the formation of products from reactants or that of reactants from products?
At equilibrium, the forward and reverse reactions occur at the same rate
If an atom of sulfur (atomic number 16) were allowed to react with atoms of hydrogen (atomic number 1), which of the molecules below would be formed? A) S-H B) H-S-H C) H=S=H D) H-S-H H E) H H-S-H H
B)
What is the maximum number of electrons in a single 2p orbital of an atom A) 1 B) 2 C) 3 D) 4 E) 5
B)
Which of the following is a correct sequence of levels in life's hierarchy, proceeding downward from an individual animal? A) organ system, tissue, molecule, cell B) nervous system, brain, nervous tissue, nerve cell C) brain, organ system, nerve cell, nervous tissue D) organism, organ system, tissue, cell, organ E) organ system, nervous tissue, brain
B)
Which of these molecules will be soluble in water? A) B) C) D) E)
B)
Which of the following is not considered to be a weak molecular interaction? A) hydrogen bond B) an ionic bond in the presence of water C) covalent bond D) both hydrogen and covalent bonds E) a van der waals interaction
C)
Explain the saying "It's not the heat, it's the humidity"
High humidity hampers cooling by suppressing the evaporation of sweat
Which two pairs of molecules in this figure are isomers? For each pair, identify the type of isomer.
The forms of C4H10 in (b) are structural isomers, as are the butanes (forms of C4H8) in (c)
How many electron pairs are shared between carbon atoms in a molecule that has the formula C2H4? A) 0 B) 1 C) 2 D) 3 E) 4
C)
You have one mol of C2H4O2, How many grams would this be equal to?(carbon = 12, oxygen = 16, hydrogen = 1) A) 29 B) 30 C) 60 D) 150 E) 342
C)
Based on your knowledge of the polarity of water molecules, the solute molecule depicted here is most likely A) non polar B) hydrophobic C) without charge D) positively charge E) negatively charge
D)
One liter of a solution of pH 2 has how many more hydrogen ions (H+) than 1 L of a solution of pH 6? A) 100,000 times more B) 40,000 times more C) 16 times more D) 10,000 times more E) 4 times more
D)
How many grams of C2H4O2 the compound in the figure above would be required to make 1 L of a 0.5 M solution? A) 60 B) 29 C) 150 D) 342 E) 30
E)
HCl is a strong acid that dissociated in water HCl -> H+ + Cl- What is the pH of 0.01 M HCl?
[H+] = 0.01 M = 10^-2 M, so pH =2
How many grams of C2H4O2 would be required to make 2.5 L of a 1 M solution? (carbon=12, oxygen=16, hydrogen=1) A) 150 B) 29 C) 30 D) 60 E) 342
A) 12x2 + 4x1 + 16x2 = 150
A water sample from a hot thermal vent contained a single celled organism that had a cell wall but lacked a nucleus. What is its most likely classification? A) Animalia B) Fungi C) Archaea D) Protista E) Eukarya
C)
Liquid water's high specific heat is mainly a consequence of the A) fact that water is a poor heat conductor B) high specific heat of oxygen and hydrogen atoms C) absorption and release of heat when hydrogen bonds break and form.ion and release of heat when hydrogen bonds break and form D) small size of the water molecules E) higher density of liquid water than solid water (ice).
C)
How many electron pairs are shared between carbon atoms in a molecule that has the formula C2H4? A) 0 B) 3 C) 1 D) 4 E) 2
E)
Given a liter of pure water and a liter solution of acetic acid, what would happen to the pH, in general, if you added 0.01 mol of a strong acid to each? Use the reaction below to explain the result HCl -> H+ + Cl-
The pH of the water should decrease from 7 to about 2; the pH of acetic acid solution will decrease only a small amount, because as a weak acid, it acts (like carbonic acid), as a buffer. The reaction CH3COOH -> CH3COO- + H+ will shift to the left, with CH3COO- accepting the influx of H+ and becoming CH3COOH molecules
Compared with a basic solution at pH 9, the same volume of an acidic solution at pH 4 has ___ times as many hydrogen ions (H+)
100,000x
Suppose you had an organic molecule such as cysteine, and you chemically removed the -NH2 group and replaced it with COOH. Draw this structure. How would this change the chemical properties of the molecule? Is the central carbon asymmetric before the change? After?
A chemical group that can act as a base has been replaced with a group that can act as an acid, increasing the acidic properties of the molecule. The shape of the molecule would also change, likely changing the molecules with which it can interact. The original cysteine molecule has an asymmetric carbon in the center. After replacement of the amino group with a carboxyl group, this carbon is no longer asymmetric
Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2 + H2O ↔ H2CO3. Carbonic acid (H2CO3) is a weak acid. Respiring cells release CO2 into the bloodstream. What will be the effect on pH of blood as that blood first comes in contact with respiring cells? A) blood pH will decrease slightly B) blood pH will first increase, then decrease as CO2 combines with hemoglobin C) blood pH will first decrease, then increase sharply as CO2 combines with hemoglobin D) blood pH will increase slightly E) blood pH will remain unchanged
A)
In comparing covalent bonds and ionic bonds, which of the following would you expect? A) covalent bonds and ionic bonds occupy opposite ends of a continuous spectrum, from nearly equal to completely unequal sharing of electrons B) ionic interactions remain when covalent bonds are broken in water. Ionic bonds are much stronger than covalent bonds C) both involve electrical attraction between the electrons of one atom and the nucleus of the other atom D) an atom can form covalent bonds with multiple partner atoms, but only a single ionic bond with a single partner atom
A)
The nucleus of a nitrogen atom contains 7 neutrons and 7 protons. Which of the following is a correct statement concerning nitrogen? A) the nitrogen atom has a mass number of 14 and an atomic mass of approximately 14 daltons. B) the nitrogen atom has a mass number of approximately 7 daltons and an atomic mass of 14. C) the nitrogen atom has a mass number of approximately 14 daltons and an atomic mass of 7. D) the nitrogen atom has a mass number of 7 and an atomic number of 14. E) the nitrogen atom has a mass number of 14 and an atomic mass of 7 grams.
A)
Two atoms appear to have the same mass number. These atoms A) must have the same number of protons and neutrons B) must have the same number of electrons C) must have the same atomic number D) must have the same atomic number, the same number of protons and neutrons, the same number of electrons, and the same chemical properties E) must have the same chemical properties
A)
Which of the following statements is true about buffer solutions? A) they maintain a relatively constant pH when either acids or bases are added to them B) they maintain a constant pH when bases are added to them but not when acids are added to them C) they maintain a constant pH when acids are added to them but not when bases are added to them D) they are found only in living systems and biological fluids E) they maintain a relatively constant pH of approximately 7 when either acids or bases are added to them
A)
Which of these provides evidence of the common ancestry of all life? A) near universality of the genetic code B) structure of the chloroplasts C) ubiquitous use of catalysts by living systems D) structure of cilia E) structure of the nucleus
A)
Which statement is true of all atoms that are anions? A) the atom has more electrons than protons B) the atom has more protons than electrons C) the atom has fewer protons than does a neutral atom of the same element D) the atom has more neutrons than protons
A)
Why does ice float in liquid water? A) hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water B) the high surface tension of liquid water keeps the ice on top C) the crystalline lattice of ice causes it to be denser than liquid water D) the ionic bonds between the molecules in ice prevent the ice from sinking E) ice always has air bubbles that keep it afloat
A)
You have two beakers. One contains pure water, the other contains pure methanol (wood alcohol). The covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules. You pour crystals of table salt (NaCl) into each beaker. Predict what will happen. A) NaCl crystals will dissolve readily in water but will not dissolve in methanol B) when the first crystals of NaCl are added to water or to methanol, they will not dissolve; but as more crystals are added, the crystals will begin to dissolve faster and faster C) NaCl crystals will NOT dissolve in either water or methanol D) equal amounts of NaCl crystals will dissolve in both water and methanol E) NaCl crystals will dissolve readily in methanol but will not dissolve in water
A)
In comparing covalent bonds and ionic bonds, which of the following would you expect? A) Covalent bonds and ionic bonds occupy opposite ends of a continuous spectrum, from nearly equal to completely unequal sharing of electrons B) Ionic interactions remain when
A) (in ionic bonds, one atom is stripped completely of an electron whereas covalent bonds share an electron equally. Covalent bonds are stronger than ionic bonds.
How can the freezing of water crack boulders?
As water freezes, it expands because water molecules move farther apart in forming ice crystals. When there is water in a crevice of a boulder, expansion due to freezing may crack the boulder
A controlled experiment is one in which: A) the experiment proceeds at a slow pace to guarantee that the scientist can carefully observe all reactions and process all experimental data B) there are at least two groups, one of which does not receive the experimental treatment C) there is one group for which the scientist controls all variables D) the experiment is repeated many times to ensure that the results are accurate E) there are at least two groups, one differing from the other by two or more variables
B)
Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2 + H2O ↔ H2CO3. Carbonic acid (H2CO3) is a weak acid. If CO2 is bubbled into a beaker containing pure, freshly distilled water, which of the following graphs correctly describes the results? A) B) C) D)
B)
If the cytoplasm of a cell is at pH 7, and the mitochondrial matrix is at pH 8, this means that A) the concentration of H+ ions is tenfold higher in the mitochondrial matrix than in the cytoplasm B) the concentration of H+ ions is tenfold higher in the cytoplasm than in the mitochondrial matrix C) the concentration of H+ ions in the cytoplasm is 8/7 the concentration in the mitochondrial matrix D) the mitochondrial matrix is more acidic than the cytoplasm E) the concentration of H+ ions in the cytoplasm is 7/8 the concentration in the mitochondrial matrix
B)
Molybdenum has an atomic number of 42. Several common isotopes exist, with mass numbers of 92, 94, 95, 96, 97, 998, and 100. Therefore, which of the following can be true? A) The isotopes of molybdenum can have between 50 and 58 protons B) Molybdenum atoms can have between 50 and 58 neutrons C) The isotopes of molybdenum have between 50 and 58 protons and have different electron configurations D) The isotopes of molybdenum have different electron configurations E) The isotopes of molybdenum have between 50 and 58 neutrons and have different electron configurations
B)
Phosphorus-32, a radioactive isotope of phosphorus-31 (atomic number 15), undergoes a form of radioactive decay whereby a neutron turns into a proton and emits radiation in the form of an electron. What is the product of such radioactive decay of phosphorus-32? A) the conversion of the phosphorus-32 atom into pure energy B) sulfur-32 (atomic number 16) C) a positively charged phosphorus-31 ion D) phosphorus-31 E) a negatively charged phosphorus-32 ion
B)
Prokaryotes are classified as belonging to two different domains. What are their domains A) Eukarya and Monera B) Bacteria and Archaea C) Bacteria and Eukarya D) Bacteria and Protista E) Archaea and Monera
B)
The reactivity of an atom arises from A) the average distance of the outermost electron shell from the nucleus B) the existence of unpaired electrons in the valence shell C) the sum of the potential energies of all the electron shells D) the potential energy of the valence shell
B)
We can represent atoms by listing the number of protons, neutrons, and electrons--for example 2p+, 2n0, 2e- for helium. Which of the following represents the 18O isotope of oxygen? A) 7p+, 2n0, 9e- B) 8p+, 10n0, 8e- C) 9p+, 9n0, 9e- D) 10p+, 8n0, 9e-
B)
You have two beakers. One contains a solution of HCl at pH = 1.0. The other contains a solution of NaOH at pH = 13. Into a third beaker, you slowly and cautiously pour 20 mL of the HCl and 20 mL of the NaOH. After complete stirring, the pH of the mixture will be A) 2.0 B) 7.0 C) 5.0 D) 9.0 E) 12.0
B)
The nutritional information on a cereal box shows that one serving of a dry cereal has 200 kilocalories. If one were to burn one serving of the cereal, the amount of heat given off would be sufficient to raise the temperature of 20 kg of water how many degrees Celsius? A) 0.2°C B) 10.0°C C) 1.0°C D) 20.0°C E) 2.0°C
B) 1 cal = energy required to raise 1 gram of water by 1 degreeC cal = (mass)(specific heat)(temp change) 200 kcal = (20 kg)( 1 cal/g*C)(X*C)
How many molecules of glucose (C6H12O6, molecular mass = 180 daltons) would be present in 90 grams of glucose? A) (90 x 6.02)e23 B) (90/180) × 6.02e23 C) 90e23 D) (6.02/90)e23 E) (6.02/90)e23
B) have 90 g of glucose molar mass of glucose (how many grams of a substance = 1 mol) Avogadro's number: 6.022 x 10^23 molecules molecular mass = 180 daltons (molar mass then = 180 g/mol because 1 Da = 1 g/mol) 90g (1mol/180g) = 0.5 mol glucose 0.5 mol (6.022 x 10^23)
How are gasoline and fat chemically similar?
Both consist largely of hydrocarbon chains, which provide fuel--gasoline for engines and fats for plant embryos and animals. Reactions of both types of molecules release energy.
About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter? A) carbon, sodium, hydrogen, nitrogen B) carbon, sodium, hydrogen, nitrogen C) carbon, hydrogen, nitrogen, oxygen D) carbon, oxygen, phosphorus, hydrogen E) oxygen, hydrogen, calcium, nitrogen
C)
In the term trace element, the adjective trace means A) the element can be used as a label to trace atoms through an organism's metabolism B) the element passes rapidly through the organism C) the element is required in very small amounts D) the element enhances health but is not essential for the organism's long-term survival
C)
One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that, when placed in an aqueous solution, dissociates into a bicarbonate ion (HCO3- and a hydrogen ion (H+). Thus, H2CO3 ↔ HCO3- + H+ If the pH of the blood increases, one would expect A) an increase in the concentration of HCO3- and a decrease in the concentration of OH- B) a decrease in the concentration of HCO3- and an increase in the concentration of H+ C) a decrease in the concentration of H2CO3 and an increase in the concentration of HCO3- D) a decrease in the concentration of HCO3- and an increase in the concentration of both H2CO3 and H+ E) an increase in the concentration of H2CO3 and a decrease in the concentration of HCO3-
C)
The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called? A) a covalent bond B) a van der Waals interaction C) a hydrogen bond D) a hydrophilic bond E) an ionic bond
C)
Which of the following best describes a model organism? A) It lends itself to many studies that are useful to beginning students B) It is small, inexpensive to raise, and lives a long time C) It is well studied, easy to grow, and results are widely applicable D) It has been chosen for study by the earliest biologists E) It is often pictured in textbooks and easy for students to imagine
C)
Which of the following is (are) true of natural selection? A) it requires genetic variation B) it results in descent with modification C) It requires genetic variation, results in descent with modification, and involves differential reproductive success D) it involves differential reproductive success E) it results in descent with modification and involves differential reproductive success.
C)
Which of these systems is least likely to be at chemical equilibrium? A) a test tube of dry organic molecules, kept at room temperature B) a test tube of organic molecules, kept in the freezer C) a test tube of living cells D) a test tube of dead cells in water, kept at room temperature E) a test tube of organic molecules dissolved in water, kept at room temperature
C)
You have a freshly prepared 0.1 M solution of glucose in water. Each liter of this solution contains how many glucose molecules? A) 3.01e23 B) 6.02e23 C) 6.02e22 D) 12.04e23 E) 6.02e24
C)
Write an equation that uses the products of photosynthesis as products. Add energy as another product. This new equation describes a process that occurs in your cells. Describe this equation in words. How does this equation relate to breathing?
C6H12O6 + 6O2 -> 6CO2 + 6H2O + Energy Glucose and Oxygen react to form carbon dioxide and water, releasing energy. We breathe in oxygen because we need it for this reaction to occur, and we breathe out carbon dioxide because it is the byproduct of this reaction (cellular respiration)
Acetic acid (CH3COOH) can be a buffer, similar to carbonic acid. Write the dissociation reaction, identifying the acid, base, H+ acceptor, and H+ donor
CH3COOH -> CH3COO- + H+ CH3COOH is the acid (the H+ donor) and CH3COO- is the base (the H+ acceptor)
What are the four main classes of large biological molecules?
Carbohydrates, lipids, proteins, nucleic acids
A covalent bond is likely to be polar when A) the two atoms sharing electrons are different elements B) one of the atoms has absorbed more energy than the other atom C) the two atoms sharing electrons are equally electronegative D) one of the atoms sharing electrons is much more electronegative than the other atom E) oxygen is one of the two atoms sharing electrons
D)
A given solution contains 0.0001(10-4) moles of hydrogen ions [H+] per liter. Which of the following best describes this solution? A) acidic: will accept H+ from both strong and weak acids B) basic: will give H+ to weak acids, but accept H+ from weak acids C) acidic: will give H+ to both strong and weak acids D) acidic: will give H+ to weak acids, but accept H+ from strong acids E) basic: will accept H+ from both strong and weak acids
D)
A strong acid like HCl A) reacts with strong bases to create a buffered solution B) both ionizes completely in aqueous solutions and is a strong buffer at low pH C) increases the pH when added to an aqueous solution D) ionizes completely in an aqueous solution E) is a strong buffer at low pH
D)
Compared with 31P, the radioactive isotope 32P has A) a different atomic number B) one more proton C) one more electron D) one more neutron
D)
Electrons exist only at fixed levels of potential energy. However, if an atom absorbs sufficient energy, a possible result is that A) the atom would become a positively charged ion, or cation, and become a radioactive isotope. B) the atom would become a negatively charged ion, or anion. C) the atom may become a radioactive isotope. D) an electron may move to an electron shell farther away from the nucleus. E) an electron may move to an electron shell closer to the nucleus.
D)
If the pH of a solution is decreased from 9 to 8, it means that the A) concentration of OH- has increased tenfold (10X) compared to what it was at pH 9 B) concentration of H+ has decreased to one-tenth (1/10) what it was at pH 9 C) concentration of OH- has decreased to one-tenth (1/10) what it was at pH 9 D) concentration of H+ has increased tenfold (10X) and the concentration of OH- has decreased to one-tenth (1/10) what they were at pH 9 E) concentration of H+ has increased tenfold (10X) compared to what it was at pH 9
D)
In a lab, which of the following constitutes an experiment? I. learning to use a microscope by examining fixed species on slides II. being able to examine swimming protists under a microscope III. extracting pigments from plant leaves and separating the types of pigments for identification IV. preparing root tips for examination by staining them A) I only B) II only C) II and III only D) III only E) II, III, and IV
D)
Nitrogen (N) is much more electronegative than hydrogen (H). Which of the following statements is correct about the atoms in ammonia (NH3)? A) the nitrogen atom has a strong positive charge; each hydrogen atom has a strong positive charge B) here are covalent bonds between the hydrogen atoms and polar bonds between each hydrogen atom and the nitrogen atom C) each hydrogen atom has a slight negative charge; the nitrogen atom has a strong positive charge D) each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge E) the nitrogen atom has a slight positive charge; each hydrogen atom has a slight negative charge
D)
Organisms interact with their environments, exchanging matter and energy. For example, plant chloroplasts convert the energy of sunlight into: A) kinetic energy B) carbon dioxide and water C) oxygen D) the potential energy of chemical bonds E) the energy of motion
D)
Prokaryotic and eukaryotic cells generally have which of the following features in common? A) a membrane bounded nucleus B) linear chromosomes made of DNA and protein C) a cell wall made of cellulose D) ribosomes E) flagella or cilia that contain microtubules
D)
The precise weight of a mole of some pure elements like silicon (Si) can vary slightly from the standard atomic mass, or even from sample to sample. Why? A) The element may undergo radioactive decay B) The atoms of the element form chemical bonds with each other, and that changes the weight of the element C) The element may react with itself and gain or lost subatomic particles D) The element may have multiple stable isotopes, and the isotopic composition may vary from sample to sample E) The amount of energy absorbed by the element affects the mass of its electrons, and thus the atomic mass can vary slightly
D)
Through time, the lineage that led to modern whales shows a change from four limbed land animals to aquatic animals with two limbs that function as flippers. This change is best explained by: A) creationism B) feedback inhibition C) the hierarchy of the biological organization of life D) natural selection E) natural philosophy
D)
Which of the following statements correctly describes any chemical reaction that has reached equilibrium A) the concentrations of products and reactants are equal B) the reaction is now irreversible C) both forward and reverse reactions have halted D) the rates of the forward and reverse reactions are equal
D)
Which of the following takes place as an ice cube cools a drink?. A) evaporation of the water in the drink increases B) a calorie of heat energy is transferred from the ice to the water of the drink C) the specific heat of the water in the drink decreases D) kinetic energy in the drink decreases E) molecular collisions in the drink increase
D)
Sulfur is in the same column of the periodic table as oxygen, but has electronegativity similar to carbon. Compared to water molecules, molecules of H2S A) will have greater cohesion to other molecules of H2S B) will ionize more readily. C) will have a higher capacity to absorb heat for the same change in temperature D) will not form hydrogen bonds with each other E) will have a greater tendency to form hydrogen bonds with each other
D) H-S-H is non polar (not a big difference in electronegativity) and non polar bonds do not form hydrogen bonds
Explain why the central water molecule can hydrogen bond to other water molecules
Due to its two polar covalent bonds, a water molecule has regions of partial negative charge on the O atom that allow it to form hydrogen bonds with hydrogen atoms on neighboring water molecules, and regions of partial positive change. on the H atoms that allow them to form hydrogen bonds with oxygen atoms on neighboring water molecules
A covalent chemical bond is one which A) outer shell electrons of one atom are transferred to fill the inner electron shell of another atom B) protons and neutrons are shared by two atoms so as to satisfy the requirements of both atoms C) electrons are removed from one atom and transferred to another atom so that the two atoms become oppositely charged D) an electron occupies a hybrid orbital located between the nuclei of two atoms E) outer shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms
E)
A small birthday candle is weighed, then lighted and placed beneath a metal can containing 100 mL of water. Careful records are kept as the temperature of the water rises. Data from this experiment are shown on the graph. What amount of heat energy is released in the burning of candle wax? A) 5 kilocalories per gram of wax burned B) 20 kilocalories per gram of wax burned C) 10 kilocalories per gram of wax burned D) 50 kilocalories per gram of wax burned E) 0.5 kilocalories per gram of wax burned
E)
Knowing just the atomic mass of an element allows inferences about which of the following? A) the number of neutrons in the element B) the chemical properties of the element C) both the number of protons and the chemical properties of the element D) the number of protons in the element E) the number of protons plus neutrons in the ele
E)
Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon? A) the change in density when it condenses to form a liquid or solid B) the release of heat by the breaking of hydrogen bonds C) the high surface tension of water D) reactions with other atmospheric compounds E) the release of heat by the formation of hydrogen bonds
E)
The illustration below shows a representation of formic acid. A formic acid molecule: A) is held together by hydrogen bonds B) has a tetrahedral shape and will form hydrogen bonds with water molecules C) has a tetrahedral configuration of hybrid electron orbitals for the carbon atom D) consists of largely non polar covalent bonds E) will form hydrogen bonds with water molecule
E)
The molar mass of glucose is 180 g/mol. Which of the following procedures should you carry out to make a 1 M solution of glucose? The molar mass of glucose is 180 g/mol. Which of the following procedures should you carry out to make a 1 M solution of glucose? A) dissolve 1 g of glucose in 1 L of water B) dissolve 180 milligrams (mg) of glucose in 1 L of water C) dissolve 180 g of glucose in 180 g of water D) dissolve 180 g of glucose in 1 L of water E) dissolve 180 g of glucose in 0.8 L of water, and then add more water until the total volume of the solution is 1 L
E)
Which drawing in the figure below depicts the electron configuration of an element with chemical properties most similar to Helium (2He)? A) B) C) D) E)
E)
Which of the following best describes the logic of scientific inquiry? A) if my experiments are set up right, they will lead to a testable hypothesis B) if I generate a testable hypothesis, tests and observations will support it C) if my observations are accurate, they will support my hypothesis D) if my prediction is correct, it will lead to a testable hypothesis E) if my hypothesis is correct, I can expect certain test results
E)
Which of the following correctly describes chemical equilibrium? A) Forward and reverse reactions have stopped so that the concentration of the reactants equals the concentration of the products. B) Reactions stop only when all reactants have been converted to products. C) There are equal concentrations of reactants and products, and the reactions have stopped. D) Concentrations of products are higher than the concentrations of the reactants. E) Forward and reverse reactions continue with no effect on the concentrations of the reactants and products.
E)
Which of the following pairs of atoms would be most likely to form a polar covalent bond?
E) (A has a two full valence shells, they would not want to participate in bonds. B would form an ionic bond because an electron would be transferred (think NaCl). C would most likely have equal sharing with no difference in electronegativity b/c it is the same atom. D would most likely form multiple bonds will be needed to satisfy the valence shells and bonds. E is showing carbon and oxygen which form a polar covalent bond. You can also see this based on the electronegativity of the two)
What is electronegativity, and how does it affect interactions between water molecules?
Electronegativity is the attraction of an atom for the electrons of a covalent bond. Because oxygen is more electronegative than hydrogen, the oxygen atom in H2O pulls electrons toward itself, resulting in two partial negative charges on the oxygen atom and a partial positive charge on each hydrogen atom. Atoms in neighboring water molecules with opposite partial charges are attracted to each other, forming a hydrogen bond
Describe how properties of water contribute to the upward movement of water in a tree
Hydrogen bonds hold neighboring water molecules together. This cohesion helps chains of water molecules move upward against gravity in water conducting cells as water evaporates from the leaves. Adhesion between water molecules and the walls of the water conducting cells also help counter gravity
The concentration of the appetite-regulating hormone ghrelin is about 1.3 x 10^-10 M in the blood of a fasting person. How many molecules of ghrelin are in 1 L of blood?
M is molarity, units of molarity are molsoluteLsoln. Thus there are 1.3⋅10−10mol per liter of blood. Furthermore, using Avogadro's number, we'll arrive at the solution: 1.3⋅10−10mol⋅6.023⋅1023 molecules mol≈7.8⋅1013 molecules
Can propane (C3H8) form isomers? Explain.
No. There is not enough diversity in the atoms. It can't form structural isomers because there is only one way for three carbons to attach to each other (in a line). There are no double bonds, so cis-trans isomers are not possible. Each carbon has at least two hydrogens attached to it, so the molecule is symmetrical and cannot have enantiomers.
What would be the effect on the properties of the water molecule if oxygen and hydrogen had equal electronegativity?
The covalent bonds of water molecules would not be polar, so no regions of the molecule would carry partial charges and water molecules would not form hydrogen bonds with each other
Why is it unlikely that two neighboring water molecules would be arranged like this?
The hydrogen atoms of one molecule, with their partial positive charges, would repel the hydrogen atoms of the adjacent molecule
A water strider (an insect that can walk on water) has legs that are coated with a hydrophobic substance. What might be the benefit? What would happen if the substance were hydrophilic?
The hydrophobic substance repels water, perhaps helping to keep the ends of the legs from becoming coated with water and breaking through he surface. If the legs were coated with a hydrophilic substance, water would be drawn up them, possibly making it more difficult for the water strider to walk on water
