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chemistry and chemical reactivity

Questions and Answers of Chemistry And Chemical Reactivity

Can carbon monoxide (Tc = 132.9 K; Pc = 34.5 atm) be liquefied at or above room temperature? Explain briefly.
Methane (CH4) cannot be liquefied at room temperature, no matter how high the pressure. Propane (C3H8), another simple hydrocarbon, has a critical pressure of 42 atm and a critical temperature of
What is surface tension? Give an example illustrating the phenomenon of surface tension. Explain why surface tension is the consequence of intermolecular forces.
When water is placed in a buret it forms a concave meniscus at the surface. In contrast, mercury (in a manometer for example) forms a convex meniscus (Figure 11.17). Explain why this phenomenon
What factors affect the viscosity of a substance? Which of the following substances, water (H2O), ethanol (CH3CH2OH), ethylene glycol (HOCH2CH2OH), and glycerol (HOCH2CH(OH)CH2OH), is expected to
If a piece of filter paper (an absorbent paper used in laboratories) is suspended above a beaker of water and just touching the surface, water will slowly move up the paper. What is the name given to
What types of intermolecular forces are important in the liquid phase of (a) CCl4, (b) CH3Cl, and(c) CH3CO2H (acetic acid)? O H₂C-C-OH acetic acid
What types of intermolecular forces are important in the liquid phase of (a) C2H6 and(b) (CH3)2CHOH?
Select the substance in each of the following pairs that should have the higher boiling point:(a) Br2 or ICl(b) neon or krypton(c) CH3CH2OH (ethanol) or C2H4O (ethylene oxide, structure below)
Use the vapor pressure curves illustrated here to answer the questions that follow.(a) What is the vapor pressure of ethanol, C2H5OH, at 60°C?(b) Considering only carbon disulfide (CS2) and ethanol,
Which of the following salts, Li2SO4 or Cs2SO4, is expected to have the more exothermic enthalpy of hydration?
Which of the following ionic compounds will have the most negative enthalpy of hydration?(a) Fe(NO3)2(b) CoCl2(c) NaCl(d) Al(NO3)3
Rank the following compounds in order of increasing molar enthalpy of vaporization: CH3OH, C2H6, HCl.
Rank the following molecules in order of increasing boiling point: CH3CH2CH2CH2CH3, CH3F, CH3Cl.
Mercury and many of its compounds are dangerous poisons if breathed, swallowed, or even absorbed through the skin. The liquid metal has a vapor pressure of 0.00169 mm Hg at 24°C. If the air in a
The following data are the equilibrium vapor pressure of limonene, C10H16, at various temperatures. (Limonene is used as a scent in commercial products.)(a) Plot these data as ln P versus 1/T so that
A “hand boiler” can be purchased in toy stores or at science supply companies. If you cup your hand around the bottom bulb, the volatile liquid in the boiler boils, and the liquid moves to the
You are going to prepare a silicone polymer, and one of the starting materials is dichlorodimethylsilane, SiCl2(CH3)2. You need its normal boiling point and to measure equilibrium vapor pressures at
The photos below illustrate an experiment you can do yourself. Place 10 mL of water in an empty soda can, and heat the water to boiling. Using tongs or pliers, turn the can over in a pan of cold
Acetone, CH3COCH3, is a common laboratory solvent. It is usually contaminated with water, however. Why does acetone absorb water so readily? Draw molecular structures showing how water and acetone
If you place 1.0 L of ethanol (C2H5OH) in a small laboratory that is 3.0 m long, 2.5 m wide, and 2.5 m high, will all the alcohol evaporate? If some liquid remains, how much will there be? The vapor
Cooking oil floats on top of water. From this observation, what conclusions can you draw regarding the polarity or hydrogen-bonding ability of molecules found in cooking oil?
Liquid ethylene glycol, HOCH2CH2OH, is one of the main ingredients in commercial antifreeze. Would you predict its viscosity to be greater or less than that of ethanol, CH3CH2OH?
Liquid methanol, CH3OH, is placed in a glass tube. Is the meniscus of the liquid concave or convex? Explain briefly.
Account for these facts:(a) Although ethanol (C2H5OH) (bp, 80°C) has a higher molar mass than water (bp, 100°C), the alcohol has a lower boiling point.(b) Mixing 50 mL of ethanol with 50 mL of
Rationalize the observation that CH3CH2CH2OH, 1-propanol, has a boiling point of 97.2°C, whereas a compound with the same empirical formula, methyl ethyl ether (CH3CH2OCH3), boils at 7.4°C.
Refer to Figure 11.8 to answer the following questions:(a) Of the three hydrogen halides (HX), which has the largest total intermolecular force?(b) Why are the dispersion forces greater for HI than
Cite two pieces of evidence to support the statement that water molecules in the liquid state exert considerable attractive force on one another.
During thunderstorms in the Midwest, very large hailstones can fall from the sky. (Some are the size of golf balls!) To preserve some of these stones, we put them in the freezer compartment of a
At the Fred Hutchison Cancer Research Center in Seattle it was discovered that mice can be put into a state of suspended animation by applying a low dose of hydrogen sulfide, H2S. The breathing rate
The figure below is a plot of vapor pressure versus temperature for dichlorodifluoromethane, CCl2F2. The enthalpy of vaporization of the liquid is 165 kJ/g, and the specific heat capacity of the
Acetaminophen is used in analgesics. A model of the molecule is shown here with its electrostatic potential surface. Where are the most likely sites for hydrogen bonding? Acetaminophen
A fluorocarbon, CF4, has a critical temperature of −45.7°C and a critical pressure of 37 atm. Are there any conditions under which this compound can be a liquid at room temperature? Explain
Shown here are models of two bases in DNA with the electrostatic potential surfaces: cytosine and guanine. What sites in these molecules are involved in hydrogen bonding with each other? Draw
In which of the following organic molecules might we expect hydrogen bonding to occur?(a) Methyl acetate, CH3CO2CH3(b) Acetaldehyde (ethanal), CH3CHO.(c) Acetone (2-propanone) (d) Benzoic acid
List four properties of liquids that are directly determined by intermolecular forces.
List the following ions in order of hydration energies: Na+, K+, Mg2+, Ca2+. Explain how you determined this order.
Compare the boiling points of the various isomeric hydrocarbons shown in the table below. Notice the relationship between boiling point and structure; branched-chain hydrocarbons have lower boiling
An 8.82-g sample of Br2 is placed in an evacuated 1.00 L flask and heated to 58.8°C, the normal boiling point of bromine. Describe the contents of the flask under these conditions.
Polarizability is defined as the extent to which the electron cloud surrounding an atom or molecule can be distorted by an external charge. Rank the halogens (F2, Cl2, Br2, I2) and the noble gases
Vapor pressures of NH3(ℓ) at several temperatures are given in the table below. Use this information to calculate the enthalpy of vaporization of ammonia. Temperature (°C) Vapor Pressure
A pressure cooker (a kitchen appliance) is a pot on which the top seals tightly, allowing pressure to build up inside. You put water in the pot and heat it to boiling. At the higher pressure, water
The data in the following table were used to create the graph shown below (P = vapor pressure of ethanol (CH3CH2OH) expressed in mm Hg, T = kelvin temperature).(a) Derive an equation for the straight
Chemists sometimes carry out reactions in liquid ammonia as a solvent. With adequate safety protection these reactions can be done at temperatures above ammonia’s boiling point in a sealed, thick
Water (10.0 g) is placed in a thick-walled glass tube whose internal volume is 50.0 cm3. Then all the air is removed, the tube is sealed, and then the tube and contents are heated to 100°C.(a)
Acetone is a common solvent. (See Study Question 8 for the structure of acetone.)(a) Allyl alcohol, CH2=CH—CH2OH, is an isomer of acetone. Acetone has a vapor pressure of 100 mm Hg at +7.7°C.
Outline a two-dimensional unit cell for the pattern shown here. If the black squares are labeled A and the white squares are B, what is the simplest formula for a “compound” based on this pattern?
Calcium metal crystallizes in a face-centered cubic unit cell. The density of the solid is 1.54 g/cm3. What is the radius of a calcium atom?
A unit cell of cesium chloride is illustrated in Figure 12.8. The density of the solid is 3.99 g/cm3, and the radius of the Cl− ion is 181 pm. Calculate the radius of the Cs+ ion in the center of
The density of copper metal is 8.95 g/cm3. If the radius of a copper atom is 127.8 pm, is the copper unit cell primitive, body-centered cubic, or facecentered cubic?
Potassium iodide has a face-centered cubic unit cell of iodide ions with potassium ions in octahedral holes. The density of KI is 3.12 g/cm3. What is the length of one side of the unit cell?
Examine the trends in lattice energy in Table 12.1. The value of the lattice energy becomes somewhat more negative on going from NaI to NaBr to NaCl, and all are in the range from −700 to −800
Predict the trend in lattice energy, from least negative to most negative, for the following compounds based on the ion charges and ionic radii: LiI, LiF, CaO, RbI.
Calculate the molar enthalpy of formation, Δf H°, of solid lithium fluoride from the lattice energy (Table 12.1) and other thermochemical data. The enthalpy of formation of Li(g), Δf H° [Li(g)]
To melt an ionic solid, energy must be supplied to disrupt the forces between ions so the regular array of ions collapses. Predict (and explain) how the melting point is expected to vary as a
Calculate the lattice enthalpy for RbCl. In addition to data in Appendices F and L, you will need the following information: AH° [Rb(g)] = 80.9 kJ/mol AfH° [RbCl(s)] = −435.4 kJ/mol
Which compound in each of the following pairs should have the higher melting point? Explain briefly.(a) NaCl or RbCl(b) BaO or MgO(c) NaCl or MgS
Considering only the molecular orbitals formed by combinations of the 2s atomic orbitals, how many molecular orbitals can be formed by 1000 Li atoms? In the lowest energy state, how many of these
How many molecular orbitals will be formed by combination of the 3s and 3p atomic orbitals in 1.0 mol of Mg atoms? At 0 K, what fraction of these orbitals will be occupied by electron pairs?
Conduction of an electric current is a general property associated with metals. How does the band theory for metallic bonding explain conductivity?
Most metals are shiny, that is, they reflect light. How does the band theory for metals explain this characteristic?
Elemental silicon and carbon (in the diamond allotropic form) have the same solid-state structure. However, diamond is an insulator and silicon is a semiconductor. Explain why there is a difference.
List the Group 4A elements in order of the size of the band gap.
Define the terms intrinsic semiconductor and extrinsic semiconductor. Give an example of each.
Is aluminum-doped silicon a p-type or an n-type semiconductor? Explain how conductivity occurs in this semiconductor.
A diamond unit cell is shown here.(a) How many carbon atoms are in one unit cell?(b) The unit cell can be considered as a cubic unit cell of C atoms with other C atoms in holes in the lattice. What
Which of the following allotropes of carbon is not a network solid?(a) Graphite(b) Diamond(c) Buckyballs (C60)(d) Graphene
The structure of graphite is given in Figure 12.19.(a) What type of intermolecular forces exist between the layers of six-member carbon rings?(b) Account for the lubricating ability of graphite. That
A soft, white waxy solid melts over a temperature range from 120°C to 130°C. It doesn’t dissolve in water and it doesn’t conduct electricity. These properties are consistent with its identity
Classify each of the following materials as falling into one of the categories listed in Table 12.2. What particles make up these solids and what are the forces of attraction between particles? Give
Classify each of the following materials as falling into one of the categories listed in Table 12.2. What particles make up these solids, and what are the forces of attraction between particles? Give
We have identified six types of solids (metallic, ionic, molecular, network, amorphous, alloys). What particles make up each of these solids and what are the forces of attraction between these
List the general properties of each type of solid.
Consider the phase diagram of CO2 in Figure 12.28.(a) Is the density of liquid CO2 greater or less than that of solid CO2?(b) In what phase do you find CO2 at 5 atm and 0°C?(c) Can CO2 be liquefied
Benzene, C6H6, is an organic liquid that freezes at 5.5°C to form beautiful, feather-like crystals. How much energy is evolved as heat when 15.5 g of benzene freezes at 5.5°C? (The enthalpy of
Use the phase diagram given here to answer the following questions:(a) In what phase is the substance found at room temperature and 1.0 atm pressure?(b) If the pressure exerted on a sample is 0.75
The specific heat capacity of silver is 0.235 J/g ∙ K. Its melting point is 962°C, and its enthalpy of fusion is 11.3 kJ/mol. What quantity of energy, in joules, is required to change 5.00 g of
Liquid ammonia, NH3(ℓ), was once used in home refrigerators as the heat transfer fluid. The specific heat capacity of the liquid is 4.7 J/g ∙ K and that of the vapor is 2.2 J/g ∙ K. The
Tungsten crystallizes in the unit cell shown here.(a) What type of unit cell is this?(b) How many tungsten atoms occur per unit cell?(c) If the edge of the unit cell is 316.5 pm, what is the radius
If your air conditioner is more than several years old, it may use the chlorofluorocarbon CCl2F2 as the heat transfer fluid. The normal boiling point of CCl2F2 is −29.8°C, and the enthalpy of
Sketch a phase diagram for O2 from the following information: normal boiling point, 90.18 K; normal melting point, 54.8 K; and triple point, 54.34 K at a pressure of 2 mm Hg. Very roughly estimate
The unit cell shown here is for calcium carbide. How many calcium atoms and how many carbon atoms are in each unit cell? What is the formula of calcium carbide? (Calcium ions are silver in color and
Silver crystallizes in a face-centered cubic unit cell. Each side of the unit cell has a length of 409 pm. What is the radius of a silver atom?
The very dense metal iridium has a face-centered cubic unit cell and a density of 22.56 g/cm3. Use this information to calculate the radius of an atom of the element.
Vanadium metal has a density of 6.11 g/cm3. Assuming the vanadium atomic radius is 132 pm, is the vanadium unit cell primitive cubic, body centered cubic, or face-centered cubic?
Calcium fluoride is the well-known mineral fluorite. Each unit cell contains four Ca2+ ions and eight F− ions. The F− ions fill all the tetrahedral holes in a face-centered cubic lattice of Ca2+
You can get some idea of how efficiently spherical atoms or ions are packed in a three-dimensional solid by seeing how well circular atoms pack in two dimensions. Using the drawings shown here, prove
Iron has a body-centered cubic unit cell with a cell dimension of 286.65 pm. The density of iron is 7.874 g/cm3. Use this information to calculate Avogadro’s number.
The solid-state structure of silicon is shown below.(a) Describe this crystal as pc, bcc, or fcc.(b) What type of holes are occupied in the lattice?(c) How many Si atoms are there per unit cell?(d)
The solid-state structure of silicon carbide is shown below.(a) How many atoms of each type are contained within the unit cell? What is the formulas of silicon carbide?(b) Knowing that the Si—C
Consider the three types of cubic units cells.(a) Assuming that the spherical atoms or ions in a primitive cubic unit cell just touch along the cube’s edges, calculate the percentage of occupied
Spinels are solids with the general formula AB2O4 (where A2+ and B3+ are metal cations of the same or different metals). The best-known example is common magnetite, Fe3O4 [which you can formulate as
Using the thermochemical data below and an estimated value of −2481 kJ/mol for the lattice energy for Na2O, calculate the value for the second electron affinity of oxygen [O−(g) + e− n
The band gap in gallium arsenide is 140 kJ/mol. What is the maximum wavelength of light needed to excite an electron to move from the valence band to the conduction band?
The conductivity of an intrinsic semiconductor increases with increasing temperature. How can this be rationalized?
Which will show the highest conductivity at 298 K, silicon or germanium?
Identify the following as either p- or n-type semiconductors.(a) Germanium doped with arsenic(b) Silicon doped with phosphorus(c) Germanium doped with indium(d) Germanium doped with antimony
Like ZnS, lead(II) sulfide, PbS (commonly called galena), has a 1∶1 empirical formula with a 2+ cation combined with the sulfide anion.Does PbS have the same solid structure as ZnS? If different,
Diamond-based semiconductors are currently of enormous interest in the research community. Although diamond itself is an insulator, the addition of a dopant will narrow the band gap. One
Calculate the lattice energy of CaCl2 using a Born- Haber cycle and data from Appendices F and L and Table 7.5.Data given in Table 7.5 TABLE 7.5 2nd Period 1st 2nd 3rd 3rd Period 1st 2nd 3rd 4th

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