Questions and Answers of Chemistry The Central Science

The following plot shows the potential energy of two Cl atoms as a function of the distance between them. (a) If the two atoms are very far away from each other, what is their potential energy
(a) An AB2 molecule is linear. How many nonbonding electron pairs are around the A atom from this information?(b) How many nonbonding electrons surround the Xe in XeF2? (c) Is XeF2 linear?
(a) An AB6 molecule has no lone pairs of electrons on the A atom. What is its molecular geometry?(b) An AB4 molecule has two lone pairs of electrons on the A atom (in addition to the four B atoms).
Ammonia, NH3, reacts with incredibly strong bases to produce the amide ion, NH2-. Ammonia can also react with acids to produce the ammonium ion, NH4+. (a) Which species (amide ion, ammonia, or
Name the proper three-dimensional molecular shapes for each of the following molecules or ions, showing lone pairs as needed: (a) ClO2- (b) SO42- (c) NF3 (d) CCl2Br2 (e) SF42+
(a) Is the molecule BF3 polar or nonpolar? (b) If you react BF3 to make the ion BF32-, is this ion planar? (c) Does the molecule BF2Cl have a dipole moment?
For each statement, indicate whether it is true or false. (a) In order to make a covalent bond, the orbitals on each atom in the bond must overlap. (b) A p orbital on one atom cannot make a
For each statement, indicate whether it is true or false. (a) The greater the orbital overlap in a bond, the weaker the bond. (b) The greater the orbital overlap in a bond, the shorter the
Consider the molecule BF3. (a) What is the electron configuration of an isolated B atom? (b) What is the electron configuration of an isolated F atom? (c) What hybrid orbitals should
Indicate whether each statement is true or false. (a) S orbitals can only make s or σ* molecular orbitals. (b) The probability is 100% for finding an electron at the nucleus in a π*
An AB3 molecule is described as having a trigonal-bipyramidal electron-domain geometry. (a) How many nonbonding domains are on atom A? (b) Based on the information given, which of the
(a) Predict the electron-domain geometry around the central Xe atom in XeF2, XeF4, and XeF6. (b) The molecule IF7 has a pentagonal bipyramid structure: five fluorines are equatorial, forming a
Sodium azide is a shock-sensitive compound that releases N2 upon physical impact. The compound is used in automobile airbags. The azide ion is N3-. (a) Draw the Lewis structure of the azide ion
The highest occupied molecular orbital of a molecule is abbreviated as the HOMO. The lowest unoccupied molecular orbital in a molecule is called the LUMO. Experimentally, one can measure the
Calicheamicin gamma-1, C55H74IN3O21S4, is one of the most potent antibiotics known: one molecule kills one bacterial cell. Describe how you would (carefully!) prepare 25.00 mL of an aqueous
A medical lab is testing a new anticancer drug on cancer cells. The drug stock solution concentration is 1.5 x 10-9 M, and 1.00 mL of this solution will be delivered to a dish containing 2.0 x 105
One of the most bizarre reactions in chemistry is called the Ugi reaction:R1C(=O)R2 + R3 - NH2 + R4COOH + R5NC →R4C(=O)N(R3)C(R1R2)C=ONHR5 + H2O(a) Write out the balanced chemical equation for the
What kind of reaction is the “water-splitting” reaction?H2O(l) → H2(g) + ½ O2(g)(a) An acid-base reaction(b) A metathesis reaction(c) A redox reaction(d) A precipitation reaction
Paclitaxel, C47H51NO14, is an anticancer compound that is difficult to make in the lab. One reported synthesis requires 11 steps, and the final yield of paclitaxel is only 5%. Assuming all steps have
The combustion of one mole of liquid ethanol, CH3CH2OH, produces 1367 kJ of heat. Calculate how much heat is produced when 235.0 g of ethanol are combusted.
Detonation of nitroglycerin proceeds as follows:4 C3H5N3O9(l) → 12 CO2(g) + 6 N2(g) + O2(g) + 10 H2O(g)(a) If a sample containing 2.00 mL of nitroglycerin (density = 1.592 g/mL) is detonated, how
Fill in the blanks in the following table: Cation Fe²+ Cr³+ Anion PO, I Formula Al2(SO4)3 MnCIO₂ Name Lithium oxide Copper(II) nitrate Ammonium carbonate Zinc perchlorate
The U.S. Mint produces a dollar coin called the American Silver Eagle that is made of nearly pure silver. This coin has a diameter of 41 mm and a thickness of 2.5 mm. The density and approximate
A U.S. 1-cent coin (a penny) has a diameter of 19 mm and a thickness of 1.5 mm. Assume the coin is made of pure copper, whose density and approximate market price are 8.9 g/cm3 and $2.40 per pound,
Which of the three subatomic particles was discovered first— the proton, neutron, or electron? Which one was discovered last?
A 25.0-cm-long cylindrical glass tube, sealed at one end, is filled with ethanol. The mass of ethanol needed to fill the tube is found to be 45.23 g. The density of ethanol is 0.789 g/mL. Calculate
In the year 2013, an estimated amount of 36 billion metric tons (1 metric ton = 1000 kg) of carbon dioxide (CO2) was emitted worldwide due to fossil fuel combustion and cement production. Express
Which separation method is better suited for separating a solution of sugar and water into pure substances, filtration or distillation?
Is the separation method used in brewing a cup of coffee best described as distillation, filtration, or chromatography?
(a) What is the electrostatic potential energy (in joules) between two protons that are separated by 62 pm? (b) What is the change in potential energy if the distance separating the two is
(a) The electrostatic force (not energy) of attraction between two oppositely charged objects is given by the equation F = k(Q1Q2/d2) where k = 8.99 x 109 N-m2/C2, Q1 and Q2 are the charges of the
A sodium ion, Na+, with a charge of 1.6 x 10-19 C and a chloride ion, Cl - , with charge of -1.6 x 10-19 C, are separated by a distance of 0.50 nm. How much work would be required to increase
A magnesium ion, Mg2+, with a charge of 3.2 x 10-19 C and an oxide ion, O2-, with a charge of -3.2 x 10-19 C, are separated by a distance of 0.35 nm. How much work would be required to increase the
The accompanying drawing shows a contour plot for a dyz orbital. Consider the quantum numbers that could potentially correspond to this orbital. (a) What is the smallest possible value of the
(a) Which of the following cannot leave or enter a closed system: heat, work, or matter? (b) Which cannot leave or enter an isolated system? (c) What do we call the part of the universe
Consider the three electronic transitions in a hydrogen atom shown here, labeled A, B, and C. (a) Three electromagnetic waves, all drawn on the same scale, are also shown. Each corresponds to
(a) According to the first law of thermodynamics, what quantity is conserved? (b) What is meant by the internal energy of a system? (c) By what means can the internal energy of a closed
Classify the following statements as either true or false: (a) In a contour representation of an orbital, such as the one shown here for a 2p orbital, the electron is confined to move about the
Can you use an approach similar to Hess’s law to calculate the change in internal energy, ΔE, for an overall reaction by summing the ΔE values of individual reactions that add up to give the
Four possible electron configurations for a nitrogen atom are shown below, but only one schematic represents the correct configuration for a nitrogen atom in its ground state. Which one is the
The speed of sound in dry air at 20 °C is 343 m/s and the lowest frequency sound wave that the human ear can detect is approximately 20 Hz. (a) What is the wavelength of such a sound
The radial probability function for a 2s orbital is shown here.Classify the following statements as either true or false: (a) There are two maxima in this function because one electron spends
(a) With reference to Figure 6.19, what is the relationship between the number of nodes in an s orbital and the value of the principal quantum number? Figure 6.19(b) Identify the number of
Does the hydrogen atom “expand” or “contract” when an electron is excited from the n = 1 state to the n = 3 state?
Two possible electron configurations for an Li atom are shown here. (a) Does either configuration violate the Pauli exclusion principle? (b) Does either configuration violate Hund’s
How many unique combinations of the quantum numbers l and ml are there when (a) n = 3, (b) n = 4?
(a) For an He+ ion, do the 2s and 2p orbitals have the same energy? If not, which orbital has a lower energy? (b) If we add one electron to form the He atom, would your answer to part (a) change?
An experiment called the Stern–Gerlach experiment helped establish the existence of electron spin. In this experiment, a beam of silver atoms is passed through a magnetic field, which deflects half
What is the maximum number of electrons in an atom that can have the following quantum numbers?(a) n = 3, ml = -2; (b) n = 4, l = 3; (c) n = 5, l = 3, ml = 2; (d) n = 4, l = 1, ml = 0.
The following do not represent valid ground-state electron configurations for an atom either because they violate the Pauli exclusion principle or because orbitals are not filled in order of
(a) What is the electrostatic potential energy (in joules) between an electron and a proton that are separated by 53 pm? (b) What is the change in potential energy if the distance separating the
Ritalin is the trade name of a drug, methylphenidate, used to treat attention-deficit/hyperactivity disorder in young adults. The chemical structure of methylphenidate is(a) Is Ritalin an acid or a
Two positively charged spheres, each with a charge of 2.0 x 10-5 C, a mass of 1.0 kg, and separated by a distance of 1.0 cm, are held in place on a frictionless track. (a) What is the
Carboxylic acids generally have pKa’s of ~5, but alcohols have pKa’s of ~16.(a) Write the acid-dissociation chemical equation for the generic alcohol ROH in water.(b) Which compounds will produce
Describe what changes occur when atmospheric CO2 interacts with the world ocean as illustrated here. CO2 (8) CO, (aq) World осean
For the molecules shown in 24.85,Data from 24.85Identify each of the functional groups in these molecules:(a)(Responsible for the odor of cucumbers)(b)(Quinine — an antimalarial drug)(c)(Indigo —
(a) Draw the condensed structural formulas for the cis and trans isomers of 2-pentene.(b) Can cyclopentene exhibit cistrans isomerism? Explain.(c) Does 1-pentyne have enantiomers? Explain.
Which statement best explains the chemical differences between DNA and RNA?(a) DNA has two different sugars in its sugar–phosphate backbone, but RNA only has one.(b) Thymine is one of the DNA
Indicate whether each statement is true or false:(a) Fatty acids are long-chain carboxylic acids.(b) Monounsaturated fatty acids have one CC single bond in the chain, while the rest are double or
Indicate whether each statement is true or false:(a) Fat molecules contain amide bonds.(b) Phosphoplipids can be zwitterions.(c) Phospholipids form bilayers in water in order to have their long
(a) What is the empirical formula of starch?(b) What is the monomer that forms the basis of the starch polymer?(c) What bond connects the monomer units in starch: amide, acid, ether, ester, or
(a) What is the empirical formula of cellulose?(b) What is the monomer that forms the basis of the cellulose polymer?(c) What bond connects the monomer units in cellulose: amide, acid, ether, ester,
(a) Are α-glucose and β-glucose enantiomers?(b) Show the condensation of two glucose molecules to form a disaccharide with an a linkage.(c) Repeat part (b) But with a β linkage.
Indicate whether each statement is true or false:(a) Disaccharides are a type of carbohydrate.(b) Sucrose is a monosaccharide.(c) All carbohydrates have the formula CnH2mOm.
Indicate whether each statement is true or false:(a) In the alpha helical structure of proteins, hydrogen bonding occurs between the side chains (R groups).(b) Dispersion forces, not hydrogen
Indicate whether each statement is true or false.(a) The sequence of amino acids in a protein, from the amine end to the acid end, is called the primary structure of the protein.(b) Alpha helix and
Draw the two possible dipeptides formed by condensation reactions between histidine and aspartic acid.
Indicate whether each statement is true or false.(a) Tryptophan is an aromatic amino acid.(b) Lysine is positively charged at pH 7.(c) Asparagine has two amide bonds.(d) Isoleucine and leucine are
(a) Draw the chemical structure of a generic amino acid, using R for the side chain.(b) When amino acids react to form proteins, do they do so via substitution, addition, or condensation
How many chiral carbons are in 2-bromo-2-chloro-3-methylpentane?(a) 0(b) 1(c) 2(d) 3(e) 4 or more.
Pure acetic acid is a viscous liquid, with high melting and boiling points (16.7°C and 118°C) compared to compounds of similar molecular weight. Suggest an explanation.
(a) Which of the following compounds, if any, is an ether?(b) Which compound, if any, is an alcohol?(c) Which compound, if any, would produce a basic solution if dissolved in water? (Assume
Indicate whether each statement is true or false.(a) Two geometric isomers of pentane are n-pentane and neopentane.(b) Alkenes can have cis and trans isomers around the CC double bond.(c) Alkynes can
Give the molecular formula of a hydrocarbon containing six carbon atoms that is(a) A cyclic alkane(b) A cyclic alkene(c) A linear alkyne(d) An aromatic hydrocarbon.
Indicate whether each statement is true or false.(a) Alkanes do not contain any carbon–carbon multiple bonds.(b) Cyclo-butane contains a four-membered ring.(c) Alkenes contain carbon–carbon
Is ammonia an organic molecule? Explain.
Indicate whether each statement is true or false.(a) Pentane has a higher molar mass than hexane.(b) The longer the linear alkyl chain for straight-chain hydrocarbons, the higher the boiling
Indicate whether each statement is true or false.(a) Butane contains carbons that are sp2 hybridized.(b) Cyclohexane is another name for benzene.(c) The isopropyl group contains three sp3-hybridized
From examination of the molecular models i–v, choose the substance that(a) Can be hydrolyzed to form a solution containing glucose(b) Is capable of forming a zwitterion(c) Is one of the four bases
The coordination complex [Cr(CO)6] forms colorless, diamagnetic crystals that melt at 90°C. (a) What is the oxidation number of chromium in this compound?(b) Given that [Cr(CO)6] is
Carbon monoxide, CO, is an important ligand in coordination chemistry. When CO is reacted with nickel metal the product is [Ni(CO)4], which is a toxic, pale yellow liquid.(a) What is the oxidation
Which transition metal atom is present in each of the following biologically important molecules:(a) Hemoglobin(b) Chlorophylls(c) Siderophores.
Give the number of (valence) d electrons associated with the central metal ion in each of the following complexes:(a) K3[Fe(CN)6](b) [Mn(H2O)6](NO3)2(c) Na[Ag(CN)2](d) [Cr(NH3)4Br2]ClO4(e)
The color and wavelength of the absorption maximum for [Ni(H2O)6]2+, [Ni(NH3)6]2+, and [Ni(en)3]2+ are given in Figure 23.30. The absorption maximum for the [Ni(bipy)3]2+ ion occurs at about 520
The colors in the copper-containing minerals malachite (green) and azurite (blue) come from a single d-d transition in each compound.(a) What is the electron configuration of the copper ion in these
The lobes of which d orbitals point directly between the ligands in(a) Octahedral geometry(b) Tetrahedral geometry?
Identify each of the following coordination complexes a either diamagnetic or paramagnetic: [Ag(NH3)2]+
Identify each of the following coordination complexes as either diamagnetic or paramagnetic:(a) [ZnCl4]2-(b) [Pd(NH3)2Cl2](c) [V(H2O)6]3+(d) [Ni(en)3]2+
(a) A complex absorbs photons with an energy of 4.51 × 10-19 J. What is the wavelength of these photons?(b) If this is the only place in the visible spectrum where the complex absorbs light, what
(a) If a complex absorbs light at 610 nm, what color would you expect the complex to be?(b) What is the energy in Joules of a photon with a wavelength of 610 nm?(c) What is the energy of this
Consider the following three complexes:(Complex 1) [Co(NH3)5SCN]2+(Complex 2) [Co(NH3)3Cl3]2+(Complex 3) CoClBr · 5NH3Which of the three complexes can have(a) Geometric isomers(b) Linkage isomers(c)
Consider the following three complexes:(Complex 1) [Co(NH3)4Br2]Cl(Complex 2) [Pd(NH3)2(ONO)2](Complex 3) [V(en)2Cl2]+Which of the three complexes can have(a) Geometric isomers(b) Linkage isomers(c)
When silver nitrate is reacted with the molecular base ortho-phenanthroline, colorless crystals form that contain the transition-metal complex shown below.(a) What is the coordination geometry of
True or false? The following ligand can act as a bidentate ligand?
Crystals of hydrated chromium(III) chloride are green, have an empirical formula of CrCl3 · 6H2O, and are highly soluble,(a) Write the complex ion that exists in this compound.(b) If the complex is
(a) Using Werner’s definition of valence, which property is the same as oxidation number, primary valence or secondary valence?(b) What term do we normally use for the other type of valence?(c) Why
Which type of substance is attracted by a magnetic field, a diamagnetic substance or a paramagnetic substance?
Among the period 4 transition metals (Sc–Zn), which elements do not form ions where there are partially filled 3d orbitals?
For each of the following compounds determine the electron configuration of the transition metal ion.(a) TiO(b) TiO2(c) NiO(d) ZnO.
Which periodic trend is responsible for the observation that the maximum oxidation state of the transition-metal elements peaks near groups 7B and 8B?(a) The number of valence electrons reaches a

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