which statement is true of ph buffers?

which statement is true of ph buffers?


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Asked by 2 years ago
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Cellsmallest unit can carry out all processes required for life Eukaryotic and Prokaryotic
Differences and Similarities of Prokaryotic and EurkaryoticDifferences Similarities eukaryotes have organelles Cytoplasm/ cytosol size Both have membranes Eukaryote: nucleus Double Helix shaped DNA Prokaryote: nucleiod region Ribosomes Prokaryote: circular Proteins Eurkaryote: linear DNA
Three DomainsArchaea Bacteria Eukaryea
Are we imposing this classification on nature?No, due to evolutionary history and our descent from a shared ancestors we are not imposing
How does DNA encode information? A. in the different shapes of the DNA molecules B. in the sequence of the nucleotides C. The gens along the length of DNA molecules encode the information for building all the cell's other molecules D. in the number of each different nucleotide E. the DNA molecule is composed of many amino acids joined together to form a functional proteinB
Which taxonomic domain includes multicellular photosynthetic organisms? A. Fungi B. Bacteria C. Archaea D. Plantae E. EukaryaE
In order for a hypothesis to be able to be used in science, which of the following must be true? A. it represents established facts B. it must be popularly accepted C. it must be proven correct D. it is testable and falsifiable E. it must be reproducibleD
Which of the following is true of a scientific theory? A. it must demonstrate the effect of one variable by testing control groups and experimental groups B. it is only accept after the person who came up with it has died C. it is formulated by many scientists over drinks at a convention D. it generates testable hypotheses, is supported by a large body evidence, and broad in scope E. it is a method or device that applies scientific knowledge for some specific purposeD
DNA is composed of building blocks called A. nucleic acid B. Gs C. nucleotides D. adenines E. amino acidsC
In eukaryotic cells DNA has the appearance of a A. single strand B. letter U C. double helix D. triple helix E. circleC
Which of the following statements is not true of scientific experiments? A. they must be well documented B. they must occur under carefully controlled conditions found in laboratory C. they yield useful results regardless of whether the hypothesis is supported or rejectedB
In an experiment, investigators try to control all of the variables except one- the one that tests the hypothesis. Which of the following reasons is the primary rationale for controlling variables in an experiment? A. to create a control group B. to enable investigators to repeat the test C. to eliminate alternative explanations for the results of an experimentC
Which of the following statements could not be supported or rejected by a scientific experiment? A. grass is green because it contains chlorophyll B. college students think football is more fun to watch than baseball C. the first living cell on Earth came from outer spaceC
Which of the following statements is true of a hypothesis? A. a hypothesis can be proved B. a hypothesis can be supported or rejected through experimentationB
Which of the following variables did Pasteur change in his experiment to test the hypothesis of spontaneous generation? A. the length of time that the flasks were allowed to sit before being sampled for organisms B. the broth used in each flask C. the shape of the flask D. the length of time that the broth was broiledC
In Pasteur's experiment to test the hypothesis of spontaneous generation, why did he boil the broth in both flask? A. to kill any existing organisms in the broth B. to provide nutrients to stimulate the growth of microorganisms C. to attract dust particles to each flask D. to expose th ebroth to a source of organismsA
What results from the Zonosemata experiment support the sub-hypothesis that wing waving alone reduces predation by jumping spiders? A. houseflies with Zonosemata wings are attacked less frequently B. untreated Zonosemata flies are attacked less frequently C. Zonosemata flies with housefly wings are attacked less frequently D. Zonosemata flis with their own wings cut and reglued are attacked less frequentlyC
Suppose that Zonosemata flies whose own wings had been clipped and reattached were attacked more frequently than untreated Zonosemata flies. How would this result affect the reliability of the other experimental results? A. all results for the experimental groups using houseflies would be invalid B. all results for the experimental groups involving wing surgery would be invalid C. all results for the experimental groups using Zonosemata flies would b invalid D. the reliability of the experimental results would not changeB
Protists and bacteria are grouped into different domains because A. protists are photosynthetic B. protists eat bacteria C. bacteria decompose protists D. bacteria are not made of cells E. protists have a membrane-bounded nucleus, which bacterial cells lackE
A controlled experiment is one that A. tests experimental and control groups in parallel B. is repeated many times to make sure the results are accurate C. is supervised by an experienced scientist D. keeps all variables constant E. proceeds slowly enough that a scientist can make careful records of the resultsA
Which of the following statements best distinguishes hypotheses from theories in science? A. hypotheses are guesses; theories are correct answers B. theories are hypotheses that have been proved C. hypotheses usually are relatively narrow in scope; theories have broad explanatory power D. theories are proved true;hypotheses are often falsified E. hypotheses and theories are essentially the same thingC
NucleotidesATGC
crystallintransparent protein
Kingdom Plantaemake own food(photosynthesis) cellulose in cell wall
Kingdom Animalianonphotosynthesis lack of cell walls
Kingdom Funginonphotosynthesis and absorb food chitin in cell wall
Diverse Protistsnot closely related to each other
Which of the following is an example of qualitative data? A. the fish swam in a zigzag motion B. the temperature decreased from 20C to 15C C. the plant's height is 25 cm D. the contents of the stomach are mixed every 20 seconds E. the six pairs of robins hatched an average of three chicksA.
Discovery Science Hypothesis Based Sciencedescribes nature through careful observations data analysis involves proposing and testing hypothesis
Which of the following best describes the logic of scientific inquiry? A. if I generate a testable hypothesis, tests and observations will support it B. if my hypothesis is correct, I can expect certain test results C. if my prediction is correct, it will lead to a testable hypothesis D. if my experiments are set up right, they will lead to a testable hypothesisB
The universal genetic language of DNA is common to virtually all organisms on Earth, however diverse. What is the best explanation for this fact? A. the universal nature of the genetic language of DNA is due to coincidence B. all living things share a common genetic language of DNA because they share a common ancestry C. the universal genetic language is explained by the chemistry of DNA and proteins D. if my observations are accurate, they will support my hypothesisB
independent variablechanged in experiment to test effects on dependent variable
control experimentcompares experimental group with a control group
dependent variable...
control group...
Elementcannot be broke down to other 92 natural elements 96% of living matter is made of four elements
trace elementrequired for life, but in smaller amounts
compoundsubstance made of two or more elements
Moleculetwo or more covalently bonded atoms same or different element
The mass number of an atom is 15, and its atomic number is 7. The atom probably has... A. about as much mass in electrons as in protons B. 7 units of negative charge in the nucleus C. at least 15 electrons D. 8 neutrons in the nucleus E. 7 elections in the nucleusD
Which statement is true of atoms? A. electrons determines the atom's size B. most of an atom's volume is filled with matter C. protons attract other protons D. protons repel electrons E. All of the aboveA
Dr. B says an atom has 3 electrons in the first shell and four electrons in the second shell. Someone should tell Dr. B that A. the second shell can't have 4 electrons B. the first shell shouldn't have 3 electrons C. the second shell should have 8 electrons D. no shell can hold more than 2 electrons E. the first shell must fill before the second shell can have electronsB
Which statement is true of the energy levels of electrons in shells? A. all the electrons in an atom have similar amounts of energy B. the valence shell has higher energy than other occupied shells C. electrons must lose energy to move from the first to the second shell D. all of the above E. none of the aboveB
Two atoms always represent the same element if they have A. the same number of protons B. the same mass number C. the same number of particles in the nucleus D. the same number of shells E. the same number of electronsA
An atom has 6 electrons, 6 protons, and 6 neutrons. You can tell that this atom belongs to the element______ because --------- A. O; because the mass number is 12 B. C;it has 6 protons C. N; it has 6 protons D. N; it has 6 electrons E. C; it has 6 electronsB
An atom has 8 protons, 8 neutrons, and 8 electrons. Another isotope of the same element might have A. 10 neutrons B. mass number 16, atomic number 7 C. 7 electrons D. 9 protons E. all the aboveA
Radioactive decay is likely to occur when A. an atom has too many neutron b. atoms collide with one another C. an electron hits the nucleus D. protons break into neutrons and electrons e. an atom has too many electronsA
Which statement is most useful in explaining why chemists assign atoms to chemical elements by counting protons? A. protons at the atom's surface determine the atom's behavior B. the nucleus doesn't change in stable isotopes C. 99% of the atom's mass consists of protons D. the proton's negative charge holds electrons in the atom E. none of the these. Elements are defined by the number of protonsA
Proton Neutron Electronp + found in the nucleus n 0 found in the nucleus e - in the shell
Covalent bonds hold atoms together because they A. fill shells without giving atoms much charge B. bring electrons closer to protons C. use forces between nuclei as well as forces between electrons D. do all of the above E. do both A and BE
In molecules, C, H, O and N atoms usually make __, __, __, and ___ bonds respectively A. 3,2,1,4 B. 2,1,3,4 C. 3,2,4,2 D. 4,1,3,2 E. 4,1,2,3E
An atom's atomic number 7. Its valence is most likely A. 1 B. 7 C. 3 D. 2 E. 5C
By making two covalent bonds, an O atom fills its valence shell. Why does the atom's charge stay close to zero? A. the charge isn't near zero, its -2 B. the atom lost electrons from other shells C. shared electrons aren't always near oxygen D. the atom has 8 electrons E. the valence shell has 6 electronsC
In a double covalent bond, a carbon atom shares A. two electrons B. both valence and nonvalence elctrons C. electrons in two orbitals D. electrons in two of its shells E. none of the aboveC
Two C atoms form a double bond. Each C is bound to two H atoms. Which statement is true? A. all the atoms lie in a plane B. the groups rotate around the C=C bond C. the bounds orient like tripods or pyramids D. all the atoms lie in a line e. the bonds orient in a tetrahedral fashionA
Partial charges occur when A. a covalent bond links atoms of two kinds B. atoms share electrons unequally C. two ions are close together D. any of the above occur E. both A and BB
To fill the valence shell an electrically neutral, unbonded atom with atomic number 8 must add A. 3 electrons B. 8 electrons C. 2 electrons D. 1 electron E. can't tell without knowing which element it isC
Which answer helps to explain why carbon atoms tend to make 4 covalent bonds? A. the valence shell needs 8 electrons B. the first electron shell has 4 orbitals C. the carbon nucleus has 4 protons D. all the above E. none of the above, carbon; makes 3 covalent bondsA
An electrically neutral molecule has the formula CHON. If the carbon atoms form the usual number of bonds, how many covalent bonds will each hydrogen atom have will other atoms in the molecule? A. 2 B. 3 C. 5 D. 1 E. 4D
Which answer correctly ranks the atoms in terms of decreasing electronegativity(highest electronegativity first)? A. O,N,C,H B. O,N,H,C C. C,H,O,N D. N,O,C,H E. N,O,H,CA
Dr. b says the O-O bond is polar and the C-C bond is nonpolar. A good student would say A. no, both bonds are highly polar B. yes, O attracts electrons more strongly than C C. Right, O is electronegative, so O is polar D. no way, C is more electronegative than O E. wrong again, Dr. B. Both bonds are nonpolarE
Use your knowledge of electronegativity to pick out the most polar bond in the list below A. N-H B. O-C C. C-H D. O-H E. O-ND
If you want a molecule that is highly polar, look for one that contains A. O-N B. S-H C. H-N D. C-S E. C-HC
Compared to covalent bonds, ionic bonds A. are more stable in water B. are more abundant in biological molecules C. have less bond energy D. rely much less on electron-sharing E. are strongerD
A cation with two units of charge has 10 neutrons and 8 protons. The ion also has A. 8 electrons B. 16 electrons C. 6 electrons D. 12 electrons E. 10 electronsC
True or false: ions may form by transferring an atomic nucleus(with or without electrons) to another moleculeTrue
A phrase that applies to covalent bonding and not other kinds of bonds is A. paired electrons B. charge attraction C. electron- sharing D. great strength E. all of the aboveC
Which statement is true of the relation between life and chemical equilibrium? A. living cells spend energy to stay close to chemical equilibrium as possible B. living cells aviod chemical equilibrium by taking energy and materials C. Life persists only if cells can stay near chemical equilibrium D. both A and C E. none of the aboveB
Which statement is true of all atoms that are anions? A. atom has more neutrons than protons B. atom has more protons than electrons C. atom has fewer protons than does a neutral atom of the same element D. the net charge is -1 E. the atom has more electrons than protonsE
Which of the following statements correctly describes any chemical reaction that has reached equilibrium? A. both forward and reverse reactions have halted B. no reactants remain C. the rates of the forward and reverse reactions are equal D. the concentrations of products and reactants are equal E. the reaction is no irreversibleC
What happens when two atoms form a chemical bond? A. two atoms fuse together to form a chemical bond B. chemical bond forms when two atoms transfer or share protons to achieve a stable nucleus C. chemical bond forms when two atoms transfer or share outer electrons to complete their outer shellC
Which of the following bonds can form between atoms of equal electronegativity? A. hydrogen bonds can form between atoms of equal electronegativity B. ionic bonds can form between atoms of equal electronegativity C. Van der Waals can form between atoms of equal electronegativityC
Radioactive Isotopes in BiologyDating fossils Chemical tracers to "tag" certain tissues/ compounds, make them detectable deliberately use to kill cancer environmental sources of radioactivity PET
Covalent Bondsatoms share electrons
Ionic bondsone atom takes an electron away from other
Polar Covalent Bondsone atom pulls electrons mroe strongly; unequal sharing
Nonpolar Covalent Bondselectrons share equally
Electronegativitytendency of an atom to pull eletrons closer
Hydrogen bondsslight attraction between partial charges of polar molecules
Van der Waals Interactionnonpolar molecules will slightly stick together if brought into close contact
Each water molecule is joined to ___ other water molecules by ___ bonds A. four; hydrogen B. two; polar covalent C. three; ionic D. four; polar covalent E. two; hydrogenA
The unequal sharing of electrons within a water molecule makes the water molecule A. hydrophobic B. polar C. change easily from a liquid to gaseous form D. ionic E. have a low surface tensionB
Polar attractions are A. forces between atoms with partial charges B. weaker than covalent bonds C. important because they are numerous D. A and B are true, C is false E. A and B and C are trueE
Hydrogen bonds A. can form between H and N B. are covalent bonds C. occur within a water molecule D. share electrons between the two bonded atoms E. all the aboveA
How many molecules does on mole contain?6.02 x 10
Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface? A. nonpolar groups attract one another B. polar groups attract one another C. nonpolar groups repel water D. polar groups repel water E. all of the aboveB
Dissolving is best described as A. breaking covalent bonds B. a mingling of molecules and/or ions C. a separation of molecules into neutral atoms D. molecules breaking into ions E. a change from a solid to a liquidB
Water is a source of ____ for chemical reactions in cells A. hydrogen atoms B. oxygen atoms C. energy D. both A and B E. A, B and CD
why doesn't oil mix with water? A. nonpolar molecules repel water molecules B. polar molecules repel nonpolar molecules C. polar molecules attract one another D. nonpolar molecules attract one another E. both A and BC
The water molecule has a bent shape because A. hydrogen atoms attract one another B. covalent bonds are never straight C. oxygen has two unbonded pairs of valence electrons D. hydrogen atoms have partial negative charge E. none of the above, water molecules are linearC
True or false the H atoms in water have partial positive charges.True
In a neutral solution the concentration of ___ A. water molecules is less than the concentration of hydroxide ions B. hydrogen ions is equal to the concentration of hydroxide ions C. water molecules is less than the concentration of hydrogen ions D. hydrogen ions is greater than the concentration of hydroxide ions E. hydrogen ions is less than the concentration fo hydroxide ionsB
About ___ molecules in a glass of water are dissociated. A. 1 in 1,000,000 B. 1 in 500,000,000 C. 1 in 5,000,000 D. 1 in 1,000,000,000 E. 1 in 2B
A compound is an acid if it A. releases ions into water B. donates H to water C. contains H D. breaks up water molecules E. take H from waterB
To determine whether a base is weak or strong A. examine the H concentration of the solution B. check the OH concentration of the solution C. look for undissociated molecules of base D. look at the acidity of the solution E. all of the aboveC
Which statement is true of pH buffers? A. they consist of strong acids and strong bases B. they keep the pH of the blood constant C. they consist of weak acids and weak bases D. both A and b E. both B and CC
A buffer consists of undissociated acid(HA) and the ion made by dissociating the acid(A). How does this system buffer a solution against decreases in pH? A. HA dissociates and releases H and A solution B. A reacts with H to become HA C. As the solution loses H, Ha replaces the H D. both A and C E. none of the aboveB
Buffers work best when A. about half of the buffer molecules are dissociated B. nearly all of the buffer molecules are undissociated C. the pH nearly neutral D. 5% nearly all of the buffer molecules are dissociated E. the ratio of H to OH is close ot 1.0A
How does the way a buffer stabilizes during addition of acid differ from the way the same buffer stabilizes pH during addition of base? A. it's the same reaction running backward or forward B. the same buffer can't work for both acid and base C. in one case the buffer is strong; in the other case it's weak D. in one case it adds H; in the other case it adds OHA
Which answer helps to explain why all living cells need pH buffers? A. hydrogen bonds only form at medium pH values B. Nuclei acids must have positive charges to form double helices C. ATP will not deliver energy if it is ionized D. Amino acid side chains have many carboxyl and amino gorupsD
To make a buffer, you need to A. combine equal amounts of a strong acid and a strong base in water B. put either a strong acid or a strong base in water C. adjust the pH to 7.0 D. have a weak acid or a weak base half ionized in water E. both A and CD
Which answer is a true statement about pH values? A. pure water has pH of 0 B. stomach juice has a high pH C. pH is important in life mainly because it affects the cohesion of water D. a high pH corresponds to a high H concentration E. none of the aboveE
What conditions must be met in order for an aqueous solution to be called "neutral"? A. there are no hydroxide ions present in the solution B. the concentrations of hydronium and hydroxide are equal C. the hydronium ion concentration is greater than the hydroxide ion concentration D. the hydroxide ion concentration is greater than the hydronium ion concentration E. none of the aboveB
Your tank of swamp fish needs a pH of 5 and the pH is 7 at present. What should you do to the H concentration? A. reduce it to 1/100 of its present value B. double it C. raise it to 100 times its present value D. raise it to 200 tiems its present value E. cut it in halfC
A solution is very acidic if it A. has a very low pH value b. has a high hydronium ion concentration C. has a very low hydronium ion concentration D. both A and B E. both A and CD
The dissociation of water A. releases free H ions into the solution B. is quickly reversed, giving neutral water molecules C. involves pairs of water molecules D. both A and B e. both B and CE
which statement
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