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chemistry
physical chemistry

Questions and Answers of Physical Chemistry

From the density of cesium chloride (3.97 g/cm3), calculate the distance between the centers of adjacent Cs+ and Cl- ions in the solid. Compare this value with the expected distance based on the
A given sample of wüstite has the formula Fe0.950O1.00. Calculate the fraction of iron ions present as Fe3+. What fraction of the sites normally occupied by Fe2+ must be vacant in this solid?
Use the relative ionic radii in Fig. 13.8 to predict the structures expected for CsBr and KF. Do these predictions agree with observed structures? The ionic radius of Cs+ is 169 pm.Figure 13.8
MnO has either the NaCl type structure or the CsCl type structure. The edge length of the MnO unit cell is 4.47 × 10–8 cm, and the density of MnO is 5.28 g/cm3. a. Does MnO crystallize in the NaCl
Superalloys have been made of nickel and aluminum. The alloy owes its strength to the formation of an ordered phase, called the gamma-prime phase, in which Al atoms are at the corners of a cubic unit
The memory metal, nitinol, is an alloy of nickel and titanium. It is called a memory metal because after being deformed, a piece of nitinol wire will return to its original shape. (See Chem. Matters,
Predict which substance in each of the following pairs would have the greater intermolecular forces. a. CO2 or OCS b. SeO2 or SO2 c. CH3CH2CH2NH2 or H2NCH2CH2NH2 d. CH3CH3 or H2CO e. CH3OH or H2CO
A mineral crystallizes in a cubic closest packed array of oxygen ions with aluminum ions in some of the octahedral holes and magnesium ions in some of the tetrahedral holes. Deduce the formula of
Perovskite is a mineral containing calcium, titanium, and oxygen. The following diagrams represent the unit cell.a. What is the formula of perovskite? b. An alternative way of drawing the unit cell
Materials containing the elements Y, Ba, Cu, and O that are superconductors (electrical resistance equals zero) at temperatures above that of liquid nitrogen were recently discovered. The structures
Define each of the following. a. Evaporation b. Condensation c. Sublimation d. Boiling e. Melting f. Enthalpy of vaporization g. Enthalpy of fusion h. Heating curve
How does each of the following affect the rate of evaporation of a liquid in an open dish? a. Intermolecular forces b. Temperature c. Surface area
Consider the following vapor pressure versus temperature plot for three different substances A, B, and C.If the three substances are CH4, SiH4, and NH3, match each curve to the correct substance.
A plot of ln(Pvap) versus 1/T (K) is linear with a negative slope. Why is this the case?
In Breckenridge, Colorado, the typical atmospheric pressure is 520 torr. What is the boiling point of water (ΔHvap = 40.7 kJ/ mol) in Breckenridge? What pressure would have to be applied to steam at
Carbon tetrachloride (CCl4) has a vapor pressure of 213 torr at 40oC and 836 torr at 80oC. What is the normal boiling point of CCl4?
The normal boiling point for acetone is 56.5oC. At an elevation of 5300 ft, the atmospheric pressure is 630 torr. What would be the boiling point of acetone (ΔHvap = 32.0 kJ/mol) at this elevation?
In each of the following groups of substances, pick the one that has the given property. Justify your answer.a. Highest boiling point: HBr, Kr, or Cl2b. Highest freezing point: H2O, NaCl, or HFc.
Plot the following data, and from the graph determine Î”Hvap for magnesium and lithium. In which metal is the bonding stronger?
From the following data for liquid nitric acid, determine its heat of vaporization and normal boiling point.
A substance has the following properties:Sketch a heating curve for the substance, starting at 250oC.
Use the heating€“cooling curve below to answer the following questions.a. What is the freezing point of the liquid? b. What is the boiling point of the liquid? c. Which is greater, the heat
How much energy does it take to convert 0.500 kg of ice at 220oC to steam at 250oC? Specific heat capacities: ice, 2.1 J g21 8C21; liquid, 4.2 Jg-1oC-1; steam, 2.0 Jg-1oC-1; ΔHvap = 40.7 kJ/ mol;
Consider a 75.0-g sample of H2O(g) at 125oC. What phase or phases are present when 215 kJ of energy is removed from this sample? (See Exercise 91.)
A 0.250-g chunk of sodium metal is cautiously dropped into a mixture of 50.0 g of water and 50.0 g of ice, both at 0oC. The reaction is 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) ΔH = –368 kJ Will the
A 20.0-g sample of ice at 210.0oC is mixed with 100.0 g of water at 80.0oC. Calculate the final temperature of the mixture assuming no heat loss to the surroundings. The heat capacities of H2O(s) and
An ice cube tray contains enough water at 22.0oC to make 18 ice cubes, each of which has a mass of 30.0 g. The tray is placed in a freezer that uses CF2Cl2 as a refrigerant. The heat of vaporization
In regions with dry climates, evaporative coolers are used to cool air. A typical electric air conditioner is rated at 1.00 × 104 Btu/ h (1 Btu, or British thermal unit, equals the amount of energy
In each of the following groups of substances, pick the one that has the given property. Justify each answer. a. highest boiling point: CCl4, CF4, CBr4 b. lowest freezing point: LiF, F2, HCl c.
Compare and contrast the phase diagrams of water and carbon dioxide. Why doesn’t CO2 have a normal melting point and a normal boiling point, whereas water does? The slopes of the solid/liquid lines
Define critical temperature and critical pressure. In terms of the kinetic molecular theory, why is it impossible for a substance to exist as a liquid above its critical temperature?
The critical point of NH3 is 132oC and 111 atm, and the critical point of N2 is –147oC and 34 atm. Which of these substances cannot be liquefied at room temperature no matter how much pressure is
Like most substances, bromine exists in one of the three typical phases. Br2 has a normal melting point of 27.2oC and a normal boiling point of 59oC. The triple point for Br2 is 27.3oC and 40 torr,
Consider the following phase diagram. What phases are present at points A through H? Identify the triple point, normal boiling point, normal freezing point, and critical point. Which phase is denser,
Use the accompanying phase diagram for sulfur to answer the following questions. (The phase diagram is not to scale.)a. How many triple points are in the phase diagram? b. What phases are in
Use the accompanying phase diagram for carbon to answer the following questions.a. How many triple points are in the phase diagram?b. What phases can coexist at each triple point?c. What happens if
Iodine, like most substances, exhibits only three phases: solid, liquid, and vapor. The triple point of iodine is at 90 torr and 115oC. Which of the following statements concerning liquid I2 must be
The melting point of a fictional substance X is 225oC at 10.0 atm. If the density of the solid phase of X is 2.67 g/cm3 and the density of the liquid phase is 2.78 g/cm3 at 10.0 atm, predict whether
Consider the following data for xenon: Triple point: ...... –121oC, 280 torr Normal melting point: ... –112oC Normal boiling point: ... –107oC Which is more dense,
Rationalize the difference in boiling points for each of the following pairs of substances:a. n-pentane CH3CH2CH2CH2CH3 36.2oCb. HF 20oC HCl €“85oC c. HCl €“85oC LiCl 1360oC d.
Some water is placed in a sealed glass container connected to a vacuum pump (a device used to pump gases from a container), and the pump is turned on. The water appears to boil and then freezes.
Oil of wintergreen, or methyl salicylate, has the following structure:Methyl 4-hydroxybenzoate is another molecule with exactly the same molecular formula; it has the following structure: Account for
You have three covalent compounds with three very different boiling points. All of the compounds have similar molar mass and relative shape. Explain how these three compounds could have very
Boron nitride (BN) exists in two forms. The first is a slippery solid formed from the reaction of BCl3 with NH3, followed by heating in an ammonia atmosphere at 750oC. Subjecting the first form of BN
Consider the following data concerning four different substances.Label the four substances as either ionic, network, metallic, or molecular solids.
A special vessel (see Fig. 16.52) contains ice and super-cooled water (both at €“10oC) connected by vapor space. Describe what happens to the amounts of ice and water as time passes.Figure
Consider a cation in a trigonal hole. What size ion will just fit in the hole if the packed spheres have radius R?
Use the diagram of the unit cell for the hexagonal closest packed structure in Fig. 16.14 to determine the net number of atoms in the hcp unit cell.Figure 16.14.
Argon has a cubic closest packed structure as a solid. Assuming that argon has a radius of 190 pm, calculate the density of solid argon.
Rubidium chloride has the sodium chloride structure at normal pressures but assumes the cesium chloride structure at high pressures. What ratio of densities is expected for these two forms? Does this
In some regions of the southwest United States, the water is very hard. For example, in Las Cruces, New Mexico, the tap water contains about 560 mg of dissolved solids per milliliter. Reverse osmosis
For each of the following solute€“solvent combinations, state the sign and relative magnitudes for Î”H1, Î”H2, Î”H3, and Î”Hsoln (as defined in
The high melting points of ionic solids indicate that a lot of energy must be supplied to separate the ions from one another. How is it possible that the ions can separate from one another when
a. Use the following data to calculate the enthalpy of hydration for calcium chloride and calcium iodide.b. Based on your answers to part a, which ion, Cl2 or I2, is more strongly attracted to water?
Although Al(OH)3 is insoluble in water, NaOH is very soluble. Explain this difference in terms of lattice energies.
Which ion in each of the following pairs would you expect to be more strongly hydrated? Why? a. Na+ or Mg2+ b. Mg2+ or Be2+ c. Fe2+ or Fe3+ d. F- or Br- e. Cl- or ClO4- f. ClO4- or SO4 2-
Write equations showing the ions present after the following strong electrolytes are dissolved in water. a. HNO3 b. Na2SO4 c. Al(NO3)3 d. SrBr2 e. KClO4 f. NH4Br g. NH4NO3 h. CuSO4 i. NaOH
For each of the following pairs, predict which substance would be more soluble in water.
Which solvent, water or carbon tetrachloride, would you choose to dissolve each of the following? a. KrF2 b. SF2 c. SO2 d. CO2 e. MgF2 f. CH2O g. CH2PCH2
Rationalize the trend in water solubility for the following simple alcohols.
In the flushing and cleaning of columns used in liquid chromatography, a series of solvents is used. Hexane (C6H14), chloroform (CHCl3), methanol (CH3OH), and water are passed through the column in
Structure, pressure, and temperature all have an effect on solubility. Discuss each of their effects. What is Henry’s law? Why does Henry’s law not work for HCl(g)? What do the terms hydrophobic
The solubility of nitrogen in water is 8.21 × 10-4 mol/ L at 0oC when the N2 pressure above water is 0.790 atm. Calculate the Henry’s law constant for N2 in units of L atm/mol for Henry’s law in
In Exercise 112 in Chapter 5, the pressure of CO2 in a bottle of sparkling wine was calculated assuming that the CO2 was insoluble in water. This was an incorrect assumption. Redo this problem by
Rationalize the temperature dependence of the solubility of a gas in terms of the kinetic molecular theory.
Calculate the sodium ion concentration when 70.0 mL of 3.0 M sodium carbonate is added to 30.0 mL of 1.0 M sodium bicarbonate. Discuss.
Which of the following will have the lowest total vapor pressure at 25oC? Which has the highest vapor pressure at 25oC? At 25oC, the vapor pressure of pure water is 23.8 torr. a. Pure water
Match the vapor pressure diagrams with the solute€“solvent combinations and explain your answers.
Is the following statement true or false? Explain your answer. When determining the molar mass of a solute using boiling-point or freezing-point data, camphor would be the best solvent choice of all
The freezing point of t-butanol is 25.50oC and Kf is 9.1oC kg/mol. Usually t-butanol absorbs water on exposure to air. If the freezing point of a 10.0-g sample of t-butanol is 24.59oC, how many grams
If the fluid inside a tree is about 0.1 M more concentrated in solute than the groundwater that bathes the roots, how high will a column of fluid rise in the tree at 25oC? Assume that the density of
Determine the van€™t Hoff factor for the following ionic solute dissolved in water.
Consider the following representations of an ionic solute in water. Which flask contains MgSO4, and which flask contains NaCl? How can you tell?
Consider the following:What would happen to the level of liquid in the two arms if the semipermeable membrane separating the two liquids were permeable to a. H2O (the solvent) only? b. H2O and solute?
A water desalination plant is set up near a salt marsh containing water that is 0.10 M NaCl. Calculate the minimum pressure that must be applied at 20oC to purify the water by reverse osmosis. Assume
A bottle of wine contains 12.5% ethanol by volume. The density of ethanol (C2H5OH) is 0.789 g/cm3. Calculate the concentration of ethanol in wine in terms of mass percent and molality.
In the winter of 1994, record low temperatures were registered throughout the United States. For example, in Champaign, Illinois, a record low of 229oF was registered. At this temperature can salting
What stabilizes a colloidal suspension? Explain why adding heat or adding an electrolyte can cause the suspended particles to settle out.
The solubility of benzoic acid,
Explain the following on the basis of the behavior of atoms and/ or ions. a. Cooking with hot water is faster in a pressure cooker than in an open pan. b. Salt is used on icy roads. c. Melted sea ice
Anthraquinone contains only carbon, hydrogen, and oxygen. When 4.80 mg of anthraquinone is burned, 14.2 mg of CO2 and 1.65 mg of H2O are produced. The freezing point of camphor is lowered by 22.3oC
A forensic chemist is given a white solid that is suspected of being pure cocaine (C17H21NO4, molar mass = 303.36 g/mol). She dissolves 1.22 + 0.01 g of the solid in 15.60 + 0.01 g of benzene. The
You add an excess of solid MX in 250 g of water. You measure the freezing point and find it to be 20.028oC. What is the Ksp of the solid?
A solid consists of a mixture of NaNO3 and Mg(NO3)2. When 6.50 g of this solid is dissolved in 50.0 g of water, the freezing point is lowered by 5.40oC. What is the composition of the solid (by
Consider an initial mixture of N2 and H2 gases that can be represented as follows.The gases react to form ammonia gas (NH3) as represented by the following concentration profile. a. Label each plot
Consider the following reactions at some temperature: 2NOCl( g) ⇌ 2NO( g) + Cl2( g) K = 1.6 × 1025 2NO( g) ⇌ N2( g) + O2( g) K = 1 × 1031 For each reaction some quantities of the reactants
Consider the following reaction: H2O( g) + CO(g) ⇌ H2( g) + CO2(g) Amounts of H2O, CO, H2, and CO2 are put into a flask so that the composition corresponds to an equilibrium position. If the CO
Consider the following reaction at some temperature:H2O(g) + CO(g) ‡Œ H2(g) + CO2(g) K = 2.0Some molecules of H2O and CO are placed in a 1.0- L container as shown below.When equilibrium is
Consider the following generic reaction: 2A2B(g) ‡Œ 2A2(g) + B2(g) Some molecules of A2B are placed in a 1.0- L container. As time passes, several snapshots of the reaction mixture are
There is only one value of the equilibrium constant for a particular system at a particular temperature, but there are an infinite number of equilibrium positions. Explain.
Explain the difference between K, Kp, and Q.
What are homogeneous equilibria? Heterogeneous equilibria? What is the difference in writing K expressions for homogeneous versus heterogeneous reactions? Summarize which species are included in K
Write expressions for K and Kp for the following reactions. a. 2NH3(g) + CO2(g) ⇌ N2CH4O(s) + H2O(g) b. 2NBr3(s) ⇌ N2(g) + 3Br2(g) c. 2KClO3(s) ⇌ 2KCl(s) + 3O2(g) d. CuO(s) + H2(g) ⇌ Cu(l) +
For which reactions in Exercise 19 is Kp equal to K? Exercise 19: a. 2NH3(g) + CO2(g) ⇌ N2CH4O(s) + H2O(g) b. 2NBr3(s) ⇌ N2(g) + 3Br2(g) c. 2KClO3(s) ⇌ 2KCl(s) + 3O2(g) d. CuO(s) + H2(g) ⇌
At a particular temperature, a 3.0- L flask contains 2.4 moles of Cl2, 1.0 mole of NOCl, and 4.5 × 10-3 mole of NO. Calculate K at this temperature for the following reaction. 2NOCl(g) ⇌ 2NO(g) +
At 1100 K, Kp 5 0.25 for the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g) What is the value of K at this temperature?
At 327oC, the equilibrium concentrations are [CH3OH] = 0.15 M, [CO] = 0.24 M, and [H2] = 1.1 M for the reaction CH3OH(g) ⇌ CO(g) + 2H2(g). Calculate Kp at this temperature.
For the reaction H2(g) + Br2(g) ⇌ 2HBr(g) Kp = 3.5 × 104 at 1495 K. What is the value of Kp for the following reactions at 1495 K? a. HBr(g) ⇌ 1/2 H2(g) + 1/2 Br2(g) b. 2HBr(g) ⇌ H2(g) +
At a particular temperature, a 2.00- L flask at equilibrium contains 2.80 × 10-4 mole of N2, 2.50 × 10-5 mole of O2, and 2.00 × 10-2 mole of N2O. Calculate K at this temperature for the reaction
The following equilibrium pressures were observed at a certain temperature for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g) PNH3 = 3.1 × 10-2 atm PN2 = 8.5 × 10-1 atm PH2 = 3.1 × 10-3 atm Calculate the

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