3/23 Questions, no bio

. (Choice A) The phase of a wave is the measure of the horizontal offset from a reference wave. When the given wave is superimposed with a copy of itself shifted by half a wavelength, it will be only partially canceled. . (Choice C) The frequency of a wave is the number of cycles that pass a fixed point per unit time. When a wave is superimposed with a copy of itself with double the frequency, both constructive and destructive interference can occur. . (Choice D) A wave summed with an exact copy of itself will result in constructive interference at all points throughout the wave.

Hearing loss due to loud environments can be mitigated with noise-canceling earphones, which generate a waveform that reduces the intensity of ambient noise through wave interference. . For the above sound wave, the waveform generated for complete noise cancellation will be: . A. phase-shifted by half a wavelength. B. flipped across the x-axis. C. double the frequency. D. the exact same wave. . . .Complete noise cancellation occurs when the generated sound wave destructively interferes with the original wave at all points, resulting in an amplitude of zero. A wave that is flipped across the x-axis will have equal and opposite amplitudes at each point along the wave. The sum of two equal and opposite amplitudes is zero, resulting in total destructive interference and canceling all noise.

(Choice A) Arginine (Arg, R) is a basic amino acid containing a guanidinium group, which is present in Compound 1. . (Choice C) Methionine (Met, M) is a nonpolar amino acid containing a thioether side chain, which is shown in Compound 3. . (Choice D) Lysine (Lys, K) is a basic amino acid that contains a four-carbon chain with a primary amine at the end of its side chain. This description corresponds to Compound 2.

Polyamines are important biologically active molecules produced in vivo by a pathway that utilizes the amino acids shown below. Which of the following amino acid abbreviations does NOT correspond to one of the given compounds? . A. Arg B. Asn C. Met D. Lys

Circular polarization occurs when two wave forms with equal amplitude and perpendicular linear polarization (ie, polarized along different axes) propagate 90° out of phase to one another (ie, one waveform yields zero displacement when the other waveform is yielding a peak or a trough). . The mismatch in phase causes each contributing wave to generate momentary oscillations that are different at every point in time. This results in a continuous rotation in the orientation of the combined wave. . A 90° phase difference is required for circular polarization because only a 90° phase shift yields both the positive and negative oscillations along each axis and the symmetry necessary to produce a circular polarization pathway.

​​​​​​​ Circularly polarized light results from the vector sum of the electric field oscillations of two linearly polarized transverse waves traveling along the same axis. . To achieve circular polarization, the two transverse waves must be out of phase to one another. The necessary phase difference is: . A. 0° B. 90° C. 180° D. 360° . . . Circular polarization refers to the rotation of polarization observed when two transverse waves with equal amplitude and perpendicular linear polarization propagate out of phase with one another by 90°.

dipole permanent dipoles dipole

A _____________ consists of opposite electric charges separated across a distance (eg, a chemical bond). . In molecules, ____________________ form across some covalent bonds due to unequal sharing of electrons between two atoms caused by significant differences in electronegativity. . In a ___________________, the region with greater electron density (ie, the more electronegative atom) gains a partial negative charge (δ−), and the region with less electron density (ie, the less electronegative atom) acquires a partial positive charge (δ+).

conjugated system Conjugation conjugation

A _______________________- can be identified by alternating single bonds and double or triple bonds, or in other words, by alternating pi bonds (p orbitals) separated by sigma bonds. . -___________________ allows for the delocalization of electron density, meaning electrons can be distributed through the alternating system's pi bonds. . In general, __________________ and electron delocalization serve to stabilize molecules such as carbanions, carbocations, and radicals by creating a more favorable charge distribution. This can be represented as multiple resonance forms of the molecule. . . . . . . . . . A conjugated system is stabilized through electron delocalization via resonance, the distribution of electrons through alternating pi bonds. Conjugated molecules can be identified by alternating single bonds and double or triple bonds.

​​​​​​​ Comparing Trial 2 to Trial 1, [A] is left unchanged but [B] is doubled and the reaction rate quadruples. This means that the rate has second-order dependence on [B] (n = 2). . Comparing Trial 3 to Trial 4, [A] is tripled but [B] is left unchanged. The rate triples, indicating that the reaction rate has first-order dependence on [A] (m = 1). Therefore, the overall reaction is third-order (m + n = 3), and the rate law can be written as: . Rate = k[A][B]^2 ⇒ k = Rate/[A][B]^2

A combination reaction was performed as described by the reaction: . A + 2B → 2C . Analysis of the kinetics for the reaction found that the reaction progress responded to changes in reagent concentration as given in the following table: . Based on the kinetic data, which of the following expressions gives the rate constant for the rate law of this reaction? . A. k= Rate/[A][B]^3 B. k=Rate/[A][B]^2 C. k=Rate/[A]^2[B] D. k=Rate/[A][B]

resonant frequency . (Choice A) From the wave velocity equation (v = λf), wavelength is inversely proportional to frequency at a given velocity. Therefore, a low-frequency sound is characterized by a long wavelength. . (Choice B) The resonant frequency depends on the physical characteristics and geometry of the object. Resonance is independent from the intensity of the sound source. . (Choice D) A phase shift is the measure of the offset of a wave from a reference wave. A phase shift does not have an effect on resonance. . Educational objective:The frequency of a sound is associated with its perceived pitch; high-frequency sounds have high pitches. The low-frequency sounds that cause resonance near the apex of the basilar membrane are characterized by low pitches.

A sound wave used in PTA that causes resonance close to the apex of the basilar membrane has a relatively: . "The cochlear spiral can be modeled as a resonator system because each section of the basilar membrane is sensitive to a specific frequency (Figure 1)." . A. short wavelength. B. high intensity. C. low pitch. D. large phase shift. . . . According to the passage, the basilar membrane is modeled as a resonator system. . The_______________________________ of an object is the frequency that causes relatively large oscillations compared to other frequencies. . The resonant frequency depends on the physical characteristics and geometry of the object. . As shown in Figure 1, high frequencies resonate near the base of the basilar membrane, and low frequencies resonate near the apex. . The frequency of a sound is associated with its perceived pitch (or tone). . A sound with a high frequency is perceived to have a high pitch, and a sound with a low frequency (such as those near the apex) is perceived to have a low pitch.

Fractional distillation, which is ideal for separating compounds with a boiling point difference <25 °C, is the best method to separate Compound 2 and acetic acid. Therefore, adding a fractionating column to the distillation setup changes the simple distillation to a fractional distillation. . The fractionating column is added between the flask and condenser to provide a larger surface area for the distillate vapors to travel before collection in the receiving flask.

A student purifies Compound 2 (102C) but discovers that a simple distillation was not successful in separating the mixture of Compound 2 and acetic acid (boiling point = 118 °C). . Which of the following changes to the simple distillation setup would allow for separation of Compound 2 and acetic acid? . A. Add a fractionating column B. Place the receiving flask in an ice bath C. Lower the position of the thermometer in the distillation setup D. Connect the distillation setup to a vacuum

amide

An _______________ is a carboxylic acid derivative with a carbonyl carbon atom bonded to an amine group, as opposed to a hydroxyl group.

imide

An ________________________ is a functional group with a nitrogen atom bound to two acyl groups (ie, two carbonyl carbon atoms). . ____________________ are structurally similar to acid anhydrides but include bonds with the acyl groups instead of oxygen atoms.

(Choice A) The propagation velocity of sound waves depend only on the properties of the medium and is unaffected by the velocity of the source. . (Choice B) The period T of a wave measures how long one cycle (or one wavelength) takes to pass through a fixed point. Because period is the inverse of frequency (T = 1/f), the observed period will decrease if the sound source is moving toward the observer. . (Choice D) The observed wavelength would increase if the source and the observer are moving away from each other.

Audiometry can also be used to evaluate a subject's ability to localize a moving sound source. When the sound source is moving toward the subject, which of the following increases? . A. The observed wave velocity B. The observed period C. The observed frequency D. The observed wavelength . . . When the sound source moves toward the observer (subject), the source generates each wave front at a location successively closer to the observer, shortening the observed wavelength. . Because the propagation velocity is unchanged, the observer detects each wave at an increased frequency (rate) compared to the source frequency. The inverse relationship between frequency and wavelength can also be explained from the wave velocity equation (v = λf).

The molecular structure of XeO3 has a central Xe atom surrounded by 4 electron domains (ie, 3 bonding domains and 1 nonbonding electron pair). Accordingly, VSEPR theory predicts the molecular geometry to be trigonal pyramidal. . The Xe=O bonds are polar due to a significant difference in electronegativity between the atoms and because the bonds have a partly complimentary orientation within the trigonal pyramidal geometry, the bond dipoles partially add together, yielding a net molecular dipole.

Based on its molecular structure, is XeO3 a polar molecule? . A. Yes, because the Xe=O bonds are polar and any molecule with polar bonds is a polar molecule. B. No, because the Xe=O bonds are nonpolar. C. Yes, because the Xe=O bonds are polar and have a geometry that gives the molecule a net dipole. D. No, because the Xe=O bonds are polar but have a geometry that causes the dipoles to cancel. . . . A molecule can be considered polar only if it has a significant net dipole. As such, the polarity of a molecule depends on the number of polar bonds present, the strength of the dipoles in each polar bond, and the shape (geometry) of the molecule. . The shape of a molecule affects its overall polarity because its geometry determines the orientations of the dipoles, and dipoles that are oriented in opposing directions can partially or fully cancel each other. . According to valence-shell electron-pair repulsion (VSEPR) theory, the shape of a molecule can be determined from its Lewis structure by distributing the electron domains as far apart as possible around a central atom to minimize electron repulsion. . A molecule's electron geometry is determined by the number of electron-dense regions, but the molecular geometry (shape) is determined by the orientations the bonded atoms adopt due to the number of bonding and nonbonding electron domains around the central atom.

In this experiment, a sample of C4H8N8O8(s) is thermally decomposed, generating enough gas to exert a pressure of 3.7 atm. . According to the stoichiometric coefficients obtained from the balanced chemical equation: . C4H8N8O8(s) → 3 CO2(g) + 1 C(s) + 2 H2O(g) + 2 H2(g) + 4 N2(g) . the complete decomposition of C4H8N8O8(s) produces 11 total moles of gas per reaction cycle. A total of 6 moles of elemental gas (2 from H2(g) and 4 from N2(g)) are generated, which is 54% of the total gas mixture, as indicated by the mole fraction of elemental gas: Xelemental gas = (nH2+nN2) / ntotal = 6 mol / 11 mol = 0.54 . The partial pressure of elemental gas can be calculated by multiplying the total pressure by the mole fraction of elemental gas: . Pelemental gas = Xelemental gas · Ptotal = 0.54·3.7 atm = 2.0atm . Therefore, H2(g) and N2(g) account for 2.0 atm of the total pressure exerted by the gas mixture.

C4H8N8O8(s) → 3 CO2(g) + C(s) + 2 H2O(g) + 2 H2(g) + 4 N2(g) . Consider the above balanced equation. If the decomposition of C4H8N8O8(s) produces a total pressure of 3.7 atm, what is the partial pressure of elemental gas? . A. 0.67 atm B. 1.3 atm C. 1.8 atm D. 2.0 atm . . . . The total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each gas component. The partial pressure of each gas component is proportional to its mole fraction.

The quinonoid intermediate (Figure 2) delocalizes the negative charge of a carbanion over a large conjugated system of pi bonds, which allows for multiple resonance forms. . In contrast, the enolate (Figure 3) delocalizes the negative charge over a relatively small region with fewer resonance forms. Therefore, the quinonoid intermediate is more stable. . (Choices A and D) The quinonoid intermediate has more resonance forms than the enolate intermediate, so the quinonoid form is more stable. . (Choice B) The increased ability of the quinonoid intermediate to delocalize electron density makes it more stable than the enolate intermediate.

Compared to the enolate intermediate shown in Figure 3, the quinonoid intermediate in Figure 2 is: . A. less stable because of its greater number of resonance forms. B. less stable because of its increased delocalization of electron density. C. more stable because of its expanded network of conjugated pi bonds. D. more stable because of its smaller number of resonance forms.

Correct answer C. . Conversion of one chiral molecule to its enantiomer often requires the formation of a planar intermediate. The reaction is stereospecific if a side group is preferentially added to one side of this intermediate.

During conversion of an amino acid from the ʟ to the ᴅ configuration in a PLP-dependent enzyme, a base removes a proton from the α-carbon. Re-protonation of the resulting planar molecule involves the nucleophilic attack of a proton donor: . A. in a nonstereospecific manner. B. on either side of the planar intermediate with equal likelihood. C. with an orientation opposite that of the proton that was removed. D. with the same orientation as the proton that was removed.

Correct answer D. . The theoretical yield is the maximum amount of a product that can be produced from a given amount of the limiting reactant initially present. . The number of moles of a product formed is proportional to the number of moles of the reactant species according to the ratios from a balanced reaction. . Molar concentrations are defined as the moles of a species per liter of solution.

If 41.4 mg of XeF4(s) is hydrolyzed in 5.00 mL of water according to Reaction 4, what is the theoretical yield of HF(aq) expressed as the molar concentration in the resulting solution? (Note: The molar mass of XeF4 is 207.28 g/mol.) . . 6 XeF4(s) + 12 H2O(l) → 2 XeO3(aq) + 4 Xe(g) + 3 O2(g) + 24 HF(aq) Reaction 4 . A. 8.00 × 10−4 M B. 1.00 × 10−2 M C. 4.00 × 10−2 M D. 1.60 × 10−1 M

From Figure 2, the hearing threshold at 1,500 Hz is 20 dB and the hearing threshold at 2000 Hz is 50 dB. Therefore, the relative intensity between the two frequencies in dB is the difference: . 20 dB−50 dB=−30 dB20 dB-50 dB=-30 dB . A sound that is 30 dB lower is 103 = 1,000 times less intense (Choice C). Alternatively, this relationship can be resolved mathematically using the definition of the logarithm. . (Choices A and B) Because the intensity of sound is measured on a logarithmic scale (not a linear scale), a change in 30 dB is not a 30-fold change in intensity. . (Choice D) Although the hearing threshold intensity for 1,500 Hz is plotted above the hearing threshold intensity for 2,000 Hz on the audiogram figure, it is important to note that the y-axis is inverted. The hearing threshold intensity at 1,500 Hz is thus lower than that for 2,000 Hz.. .

In Figure 2, how does the hearing threshold intensity at 1,500 Hz compare to the threshold intensity at 2,000 Hz? . A. It is 30 times less intense. B. It is 30 times more intense. C. It is 1,000 times less intense. D. It is 1,000 times more intense.

(Choice A) Although the electron affinity of Xe is close to zero, this property does not determine the polarity of a chemical bond between two atoms. . (Choice B) The electronegativities of Xe and O cannot be nearly equal because their positions on the periodic table (relative to fluorine) are very different. . (Choice C) Although the Xe=O bonds are polar, the polarity results from the electronegativity of Xe being much lower than the electronegativity of O. . Educational objective:The difference in electronegativity between two bonded atoms determines the polarity of the bond between the atoms. Greater separation between two elements on the periodic table usually indicates a greater difference in electronegativity and a larger dipole moment (higher polarity).

In XeO3, the xenon-oxygen bonds are: . A. nonpolar, because the electron affinity of Xe is close to zero. B. nonpolar, because the electronegativities of Xe and O are nearly equal. C. polar, because the electronegativity of Xe is much higher than the electronegativity of O. D. polar, because the electronegativity of Xe is much lower than the electronegativity of O. . . . . Covalent bonds form when two atoms (usually nonmetals) share electrons. If the electronegativities of two covalently bonded atoms are significantly dissimilar, then the electrons are shared unequally between the bonded atoms and a dipole is formed, producing a polar covalent bond. . Conversely, if the electronegativities of the bonded atoms are very similar, the bond is nonpolar. . On the periodic table, electronegativity tends to increase across a row and decrease down a column. . Although noble gases are usually excluded from electronegativity tables (because these elements rarely form bonds), the electronegativity trend still holds true for the noble gas group. . As such, Xe has a significantly lower electronegativity than O because Xe is a little farther to the right but much lower on the periodic table than O. . Therefore, the Xe=O bonds in XeO3 are polar because the electronegativity of Xe is much lower than the electronegativity of O.

Decarboxylation is the removal of a carboxyl group from a compound; the removed carboxyl group is converted to CO2. . According to the question, some PLP-dependent enzymes participate in the decarboxylation of α-amino acids by stabilizing a carbanion intermediate (Number II), similar to the mechanism shown in Figure 2. . After formation of the carbanion, a proton can be added by a mechanism similar to that of step 4 of Figure 2 to neutralize the negative charge (Number III). . (Number I) This structure has not been decarboxylated. . Educational objective:Decarboxylation is the removal of a carboxyl group with the release of CO2.

In addition to its role in many racemases, PLP acts as a coenzyme to help decarboxylate certain amino acids by helping stabilize a carbanion. Which of the following structures could be intermediates of this mechanism after decarboxylation has occurred? . A. I only B. II only C. II and III only D. I, II, and III

Dipole-dipole Ion-dipole Dipole-induced dipole Dipole-dipole London dispersion forces

Many intermolecular forces (ie, noncovalent interactions between atoms and molecules) involve the partial charges of bond dipoles. . A____________________________ interaction occurs when the opposite partial charges of the permanent dipoles of the polar bonds in neighboring molecules form a mutual attraction. . _____________________ interactions occur between the partial charge of a permanent dipole and the full charge of an ion. . _________________________ interactions occur when a permanent dipole induces a weak temporary dipole in a nonpolar bond or atom. . _______________________ interactions occur between the partial charges of two permanent dipoles. . _________________________ occur between momentary induced dipoles cause by orbital distortions.

T-shaped geometry

Name it

Tetrahedral

Name it

Trigonal planar geometry

Name it

Trigonal pyramidal

Name it

The structure of an imine is comparable to that of a ketone in that they both contain a carbon-heteroatom double bond. Imines are composed of a carbon-nitrogen double bond with either a hydrogen atom or an R group attached to the nitrogen atom. Imines that contain an R group on the nitrogen atom are known as Schiff bases. . The Schiff base shown in Figure 1 contains a carbon-nitrogen double bond (C=N) and therefore is an example of an imine. . Choice BHowever, tautomerization is not possible in the given Schiff base because no hydrogen atom is available on the carbon adjacent to the C=N to migrate to the nitrogen atom.

The Schiff base shown in Figure 1 contains which of the following functional groups? . A. Amide B. Enamine C. Imide D. Imine

x Therefore, the resonant wavelength is twice the given length L = 0.25 m of the stethoscope: . λ=2L = 20*0.25 m = 0.5 m . From the wave velocity equation, the velocity v of a wave is the product of its wavelength λ and frequency f: . v=λ/f . Therefore, the frequency of the wave is the given speed of sound v = 350 m/s divided by λ = 0.5 m: . f=v/λ=350 m/ s0.5 m = 700 Hz . From Figure 1, a frequency of 700 Hz would cause the basilar membrane to resonate around 25 mm from it base.

The earliest stethoscope was simply a wooden pipe open at both ends. The fundamental frequency of a 0.25-m stethoscope will cause resonance at approximately what distance along the basilar membrane from its base? (Note: Use 350 m/s for the speed of sound in air.) . A. 7 mm B. 16 mm C. 25 mm D. 32 mm

Based on Table 1, Compound 3 is the ester with the pineapple scent and is made from butanoic acid and ethanol. . The prefixbut- indicates the carboxylic acid has four carbons and the prefix eth- indicates the alcohol has two carbons. . Therefore, when butanoic acid and ethanol react, the portion of the resulting ester containing the carbonyl has four carbons and the carbon chain bonded to the oxygen atom has two carbons. . The ester given in this question shows the reverse: the portion of the ester containing the carbonyl has two carbons and the carbon chain bonded to the oxygen atom has four carbons. . Therefore, the given ester is not Compound 3, the ester with a pineapple scent.

The structure of an ester is shown below. Does this structure correspond to the ester that has a pineapple scent as described in Table 1? . A. Yes, because this is the structure of Compound 3, which is made from a four-carbon carboxylic acid and a two-carbon alcohol. B. No, because this ester was made from a two-carbon carboxylic acid and a four-carbon alcohol and does not correspond to Compound 3. C. Yes, because this is the structure of Compound 3, which is made from a two-carbon carboxylic acid and a four-carbon alcohol. D. No, because this is the structure of Compound 2, which has a pear scent.

Using the equation for power and substituting the corresponding I and V gives: . I1V1>I2V2>I3V3 . I V1>IV2>IV3 . V1>V2>V3 Therefore, the current through each bulb is equal, the brightest bulb must have the greatest V, and the dimmest bulb must have the smallest V. . (Choices B, C, and D) The current flow through each bulb is equal. However, the voltage drop is greatest across bulb 1 and smallest across bulb 3. . Educational objective:Current flow is equal through all elements of a series circuit. Light bulb brightness is proportional to electric power, which is the product of the current and voltage.

Three different light bulbs of varying brightness are connected in series to a voltage source. Bulb 1 is the brightest, and bulb 3 is the dimmest. The voltages across the bulbs, V1, V2, and V3, are related by which of the following? . A. V1>V2>V3 B. V1=V2=V3 C. V3=V1>V2 D. V3>V2>V1

Reaction 1 shows the Fisher esterification between acetic acid and isoamyl alcohol. Based on the structure of isoamyl alcohol given in the reaction scheme, the parent chain contains four carbons (prefix but-) and is numbered so the hydroxyl group is given the lowest position number possible (carbon 1). There is a methyl substituent on carbon 3. Therefore, the IUPAC name of isoamyl alcohol is 3-methylbutan-1-ol. . Alcohols are molecules containing a hydroxyl group (-OH) and are named using the suffix -ol. The prefix indicates the length of the parent chain (longest continuous carbon chain containing the hydroxyl group), and the position of the hydroxyl group is indicated by its position number before the suffix.

What is the IUPAC name of isoamyl alcohol based on the structure shown in Reaction 1? . A. 3-Methylbutan-1-ol B. 2-Methylbutan-4-ol C. 2-Isopropylethan-1-ol D. 3,3-Dimethylpropan-1-ol

In the formation of XeO3, Xe contributes 8 valence electrons, and each of the three O atoms contributes 6 valence electrons (ie, a total of 8 + 6 + 6 + 6 = 26 valence electrons). . This results in a molecular structure with a central Xe atom surrounded by 4 electron domains (ie, 3 bonding domains and 1 nonbonding electron pair). . Although the Xe atom can be drawn with an "expanded octet" by forming double bonds to minimize charges, the arrangement of electron domains remains the same.

What is the molecular geometry of a XeO3 molecule? . A. Trigonal planar B. T-shaped C. Trigonal pyramidal D. Tetrahedral

The passage states that the students verified the reaction product by electron-impact mass spectrometry, in which the molecule is ionized by the removal of an electron. . The resulting ion is the molecular ion (M+) and is a radical cation with a mass-to-charge ratio (m/z) equal to the molecular weight of the molecule because the mass of the electron lost is negligible. . Table 1 shows that Compound 2 was prepared by a condensation reaction between acetic acid and propanol. . Because condensation reactions join two compounds together, resulting in the loss of water, the molecular weight of Compound 2 is obtained by adding together the molecular weights of acetic acid and propanol given in the question and subtracting the molecular weight of water (18 g/mol): Compound 2 molecular weight = 60 g/mol + 60 g/mol - 18 g/mol = 102 g/mol . Therefore, the expected m/z for the M+ for Compound 2 is 102.

When a student uses mass spectrometry to verify that they made Compound 2 which is acetic acid with propanol, what is the expected m/z of the molecular ion peak (M+) for Compound 2? (Note: Acetic acid and propanol each have a molecular weight of 60 g/mol.) . A. 60 B. 102 C. 120 D. 138

(Choices A and C) The intensity of sound waves decrease when passing from air to a solid structure because a portion of the wave is reflected at the interface between the two structures. . (Choice B) The velocity of sound increases as it moves from air to the tympanic membrane because sound velocity is fastest in solids. . When sound moves from one medium to another, a portion of its energy is reflected, decreasing its intensity. The propagation velocity of sound depends on the medium and is slowest in gases, faster in liquids, and fastest in solid

When sound passes from air to the tympanic membrane, what changes occur to the sound's intensity and velocity? . A. Both increase B. Both decrease C. Intensity increases; velocity decreases D. Intensity decreases; velocity increases . . . When a wave moves from one medium to another, its frequency does not change. . Changes in wave velocity only cause the wavelength to change. The propagation velocity of sound waves depends on the properties of the medium: . Velocity increases with temperature. . Velocity is slowest in gases, faster in liquids, and fastest in solids. . Within a phase of matter, velocity increases with stiffness and decreases with density. . Therefore, when sound passes from air to a solid (such as the tympanic membrane), its propagation velocity increases.

The representative elements (also called the main group elements) are the elements in Groups 1-2 and Groups 13-18 on the periodic table. These elements are so called because they are the most abundant elements in nature and provide a wide representation of the elemental and chemical characteristics found in natural systems.. . (Choice A) Group 1 (1A) is part of the s-block elements and is included in the representative elements. . (Choices C and D) Group 13 (3A) and Group 18 (8A) are part of the p-block elements and are included in the representative elements. . Educational objective:The representative elements (main group elements) are the elements in Groups 1-2 (1A-2A) and Groups 13-18 (3A-8A) that are contained in the s-block and the p-block, respectively, of the periodic table.

Which of the following element groups is NOT included in the representative elements? . A. Group 1 B. Group 3 C. Group 13 D. Group 18

In the structures of 15-crown-5 and XeO3, the C-O and Xe=O bonds are all polar and have permanent dipoles. As such, the opposite partial charges of these bonds can align and participate in dipole-dipole interactions. . Therefore, primarily dipole-dipole forces cause the mutual attractions between 15-crown-5 and XeO3. . As the atoms are drawn closer together by these attractions, coordinate covalent bonds are formed and result in the production of the (15-crown-5)-XeO3 complex.

Which of the following intermolecular forces primarily cause the attractions between 15-crown-5 and XeO3 that result in the formation of the coordinate covalent bonds present in the (15-crown-5)-XeO3 complex? . A. London dispersion forces B. Dipole-dipole forces C. Dipole-induced dipole forces D. Ion-dipole forces

Correct answer A. . The balanced net reaction for a chemical process involving more than one step may be found by taking the sum of the reactions for each step. Multiples of one or more reactions may be needed to achieve an overall atom balance. Species matching in type and number on both sides of the summation cancel from the net reaction.

Which of the following is the net reaction for the hydrolysis and complexation of a mixture of 6 moles XeF4 and 1 mole of XeF6 following Reactions 3, 4, and 5? (Note: Y = 15-crown-5.) . A. XeF6 + 6 XeF4 + 15 H2O + 3 Y → 4 Xe + 3 O2 + 30 HF + 3 YXeO3 B. XeF6 + 6 XeF4 + 15 H2O + Y → 6 Xe + 3 O2 + 30 HF + YXeO3 C. 6 XeF4 + 12 H2O + Y + XeO3 → 4 Xe + 3 O2 + YXeO3 + 24 HF D. XeF6 + 6 XeF4 + 15 H2O → 3 XeO3 + 4 Xe + 3 O2 + 30 HF

The side chain of glutamate, also known as glutamic acid (Glu, E), consists of two straight-chain carbon atoms bonded to a carboxylic acid. . The structure in Choice B shows ʟ-glutamate, which has an S configuration at the α-carbon . ​​​​​​​ (Choice A) Since this structure has an R configuration, it is ᴅ-glutamate, the product of the reaction. . (Choices C and D) These structures correspond to asparagine (Asn, N). The side chain of asparagine has one less carbon atom than glutamate and contains an amide rather than a carboxylic acid. . ​​​​​​​Of the 19 common ʟ-amino acids, all have an S configuration except for cysteine (glycine is achiral). The absolute configuration of R or S enantiomers is determined by the priority of groups attached to a chiral carbon.

Which of the following structures is the substrate for the reaction catalyzed by glutamate racemase? . . Racemase convert L-amino acids to d-amino acids.

1,000,000/100 parts = 10,000/1% . . 0.90% NaCl * 10,000/1% = 9000 ppm NaCl

Which of the following values gives the number of parts per million (ppm) of NaCl in a 0.90% saline solution? . A. 900 B. 9,000 C. 90,000 D. 900,000

Intensity . The intensity of sound is measured on a logarithmic scale with units of decibels (dB). For each decrease in 10 dB, the sound intensity decreases by a factor of 10. Therefore, a decrease in 30 dB is equal to a 1,000-fold decrease in intensity.

_______________ is defined as the amount of power (energy per unit time) delivered per unit area. . . I = Power/area = energy/area The intensity of sound is related to its perceived loudness and is approximately logarithmic; a ten-fold increase in sound intensity is perceived to be twice as loud. The ratio of the intensities of two sounds is measured on a base-10 logarithmic scale with units of decibels (dB): [dB]=10log(I1/I2) . log10 Y = x y = 10^x For every increase in 10 dB, the ratio of the intensities increases by a factor of 10 (eg, +20 dB = 102 = 100 times more intense). Conversely, the ratio of the intensities decreases by a factor of 10 for each decrease in 10 dB.

Enamines enamines

_________________ are functional groups that contain an amine group bonded to an alkene. . Many imines can be converted to _______________ through tautomerization. .

Polarization polarized circularly right-polarized left-polarized

_________________ is a property unique to transverse waves (eg, electromagnetic radiation) in which the wave oscillations are aligned in a particular spatial orientation within the x,y,z-coordinate system. . When two _____________________ waves combine, a new wave is formed with a different polarization. . For example, a wave polarized along the x-axis totally in-phase with a wave polarized along the y-axis produces a combined wave that is polarized between the x- and y-axes at a 45° angle. . When the polarization of a combined wave rotates around the axis of propagation, the wave is said to be _________________ polarized. . If the polarization of the combined wave rotates in a clockwise direction when viewed facing the direction of propagation, the waveform is _____________________; if the polarization rotates in a counterclockwise direction, the waveform is ____________________.