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chemistry
physical chemistry

Questions and Answers of Physical Chemistry

You are given ΔH for a process that occurs at constant pressure. What additional information do you need to determine ΔE for the process?
Suppose that the gas-phase reaction 2 NO(g) + O2(g) → 2 NO2(g) were carried out in a constant-volume container at constant temperature. Would the measured heat change represent ΔH or ΔE? If there
A gas is confined to a cylinder under constant atmospheric pressure, as illustrated in Figure 5.4.When the gas undergoes a particular chemical reaction, it absorbs 824 J of heat from its surroundings
A gas is confined to a cylinder under constant atmospheric pressure, as illustrated in Figure 5.4.When 0.49 kJ of heat is added to the gas, it expands and does 214 J of work on the surroundings. What
The complete combustion of ethanol, C2H5OH(l), to form H2O(g) and CO2(g) at constant pressure releases 1235 kJ of heat per mole of C2H5OH. (a) Write a balanced thermo-chemical equation for this
The contents of the closed box in each of the following illustrations represent a system, and the arrows show the changes to the system during some process. The lengths of the arrows represent the
The decomposition of slaked lime, Ca(OH)2(s), into lime, CaO(s), and H2O(g) at constant pressure requires the addition of 109 kJ of heat per mole of Ca(OH)2. (a) Write a balanced thermo-chemical
Ozone, O3(g), is a form of elemental oxygen that is important in the absorption of ultraviolet radiation in the stratosphere. It decomposes to O2(g) at room temperature and pressure according to the
Without referring to tables, predict which of the following has the higher enthalpy in each case: (a) 1 mol CO2(s) or 1 mol CO2(g) at the same temperature, (b) 2 mol of hydrogen atoms or 1 mol of
Consider the following reaction: (a) Is this reaction exothermic or endothermic? (b) Calculate the amount of heat transferred when 3.55 g of Mg(s) reacts at constant pressure. (c) How many grams of
Consider the following reaction: 2 CH3OH(g) → 2 CH4(g) + O2(g).............ΔH = + 252.8 kJ (a) Is this reaction exothermic or endothermic? (b) Calculate the amount of heat transferred when 24.0 g
When solutions containing silver ions and chloride ions are mixed, silver chloride precipitates: (a) Calculate ΔH for production of 0.450 mol of AgCl by this reaction. (b) Calculate ΔH for the
At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat KClO3:For this reaction, calculate Î”H for the formation of (a) 1.36 mol of O2 (b) 10.4
Consider the combustion of liquid methanol, CH3OH(l):(a) What is the enthalpy change for the reverse reaction? (b) Balance the forward reaction with whole-number coefficients. What is Î”H
Consider the decomposition of liquid benzene, C6H6(l), to gaseous acetylene, C2H2(g):(a) What is the enthalpy change for the reverse reaction? (b) What is Î”H for the formation of 1 mol of
(a) What are the units of molar heat capacity? (b) What are the units of specific heat? (c) If you know the specific heat of copper, what additional information do you need to calculate the heat
Imagine that you are climbing a mountain. (a) Is the distance you travel to the top a state function? Why or why not? (b) Is the change in elevation between your base camp and the peak a state
Two solid objects, A and B, are placed in boiling water and allowed to come to temperature there. Each is then lifted out and placed in separate beakers containing 1000 g water at 10.0 °C. Object A
(a) What is the specific heat of liquid water? (b) What is the molar heat capacity of liquid water? (c) What is the heat capacity of 185 g of liquid water? (d) How many kJ of heat are needed to raise
(a) Which substance in Table 5.2 requires the smallest amount of energy to increase the temperature of 50.0 g of that substance by 10 K? (b) Calculate the energy needed for this temperature change.
The specific heat of octane, C8H18(l), is 2.22 J g-K. (a) How many J of heat are needed to raise the temperature of 80.0 g of octane from 10.0 °C to 25.0 °C? (b) Which will require more heat,
Consider the data about gold metal in Exercise 5.28(b). (a) Based on the data, calculate the specific heat of Au(s). (b) Suppose that the same amount of heat is added to two 10.0-g blocks of metal,
When a 6.50-g sample of solid sodium hydroxide dissolves in 100.0 g of water in a coffee-cup calorimeter (Figure 5.18), the temperature rises from 21.6 °C to 37.8 °C. Calculate ¢H (in kJ/mol NaOH)
(a) When a 4.25-g sample of solid ammonium nitrate dissolves in 60.0 g of water in a coffee-cup calorimeter (Figure 5.18), the temperature drops from 22.0 °C to 16.9 °C. Calculate ΔH (in kJ/mol
A 2.200-g sample of quinone (C6H4O2) is burned in a bomb calorimeter whose total heat capacity is 7.854 kJ/°C. The temperature of the calorimeter increases from 23.44°C to 30.57°C. What is the
A 1.800-g sample of phenol (C6H5OH) was burned in a bomb calorimeter whose total heat capacity is 11.66 kJ/°C. The temperature of the calorimeter plus contents increased from 21.36 °C to 26.37
Under constant-volume conditions, the heat of combustion of glucose (C6H12O6) is 15.57 kJ/g. A 3.500-g sample of glucose is burned in a bomb calorimeter. The temperature of the calorimeter increased
The diagram shows four states of a system, each with different internal energy, E.(a) Which of the states of the system has the greatest internal energy?(b) In terms of the Î”E values,
Under constant-volume conditions, the heat of combustion of benzoic acid (C6H5COOH) is 26.38 kJ/g. A 2.760-g sample of benzoic acid is burned in a bomb calorimeter. The temperature of the calorimeter
What is the connection between Hess's law and the fact that H is a state function?
Consider the following hypothetical reactions:(a) Use Hess's law to calculate the enthalpy change for the reaction A †’ C. (b) Construct an enthalpy diagram for substances A, B, and C, and
Calculate the enthalpy change for the reactionP4O6 + 2 O2(g) †’ P4O10(s)given the following enthalpies of reaction:
From the enthalpies of reactionCalculate Î”H for the reaction
From the enthalpies of reactioncalculate Î”H for the reaction of ethylene with F2:
Given the datause Hess's law to calculate Î”H for the reaction
(a) What is meant by the term standard conditions with reference to enthalpy changes? (b) What is meant by the term enthalpy of formation? (c) What is meant by the term standard enthalpy of formation?
(a) Why are tables of standard enthalpies of formation so useful? (b) What is the value of the standard enthalpy of formation of an element in its most stable form? (c) Write the chemical equation
For each of the following compounds, write a balanced thermochemical equation depicting the formation of one mole of the compound from its elements in their standard states and use Appendix C to
You may have noticed that when you compress the air in a bicycle pump, the body of the pump gets warmer. (a) Assuming the pump and the air in it comprise the system, what is the sign of w when you
Write balanced equations that describe the formation of the following compounds from elements in their standard states, and use Appendix C to obtain the values of their standard enthalpies of
The following is known as the thermite reaction [Figure 5.8(b)]:This highly exothermic reaction is used for welding massive units, such as propellers for large ships. Using standard enthalpies of
Many portable gas heaters and grills use propane, C3H8(g), as a fuel. Using standard enthalpies of formation, calculate the quantity of heat produced when 10.0 g of propane is completely combusted in
Using values from Appendix C, calculate the standard enthalpy change for each of the following reactions: (a) 2 SO2(g) + O2(g) → 2 SO3(g) (b) Mg(OH)2 (s) → MgO (s) + H2O(I) (c) N2O4(g) + 4 H2(g)
Using values from Appendix C, calculate the value of ΔH° for each of the following reactions: (a) CaO(s) + 2 HCl(g) → CaCl2(s) + H2O(g) (b) 4 FeO(s) + O2(g) → 2 Fe2O3(s) (c) 2 CuO(s) + NO(g)
Complete combustion of 1 mol of acetone (C3H6O) liberates 1790 kJ:Using this information together with data from Appendix C, calculate the enthalpy of formation of acetone.
Calcium carbide (CaC2) reacts with water to form acetylene (C2H2) and Ca(OH)2. From the following enthalpy of reaction data and data in Appendix C, calculate Î”Hf° for CaC2(s):
Gasoline is composed primarily of hydrocarbons, including many with eight carbon atoms, called octanes. One of the cleanest-burning octanes is a compound called 2,3,4- trimethylpentane, which has the
Diethyl ether, C4H10O(l), a flammable compound that has long been used as a surgical anesthetic, has the structure CH3 ¬ CH2 ¬ O ¬ CH2 ¬ CH3 The complete combustion of 1 mol of C4H10O(l) to
Ethanol (C2H5OH) is currently blended with gasoline as an automobile fuel. (a) Write a balanced equation for the combustion of liquid ethanol in air. (b) Calculate the standard enthalpy change for
In the accompanying cylinder diagram a chemical process occurs at constant temperature and pressure.(a) Is the sign of w indicated by this change positive or negative?(b) If the process is
Methanol (CH3OH) is used as a fuel in race cars. (a) Write a balanced equation for the combustion of liquid methanol in air. (b) Calculate the standard enthalpy change for the reaction, assuming
(a) What is meant by the term fuel value? (b) Which is a greater source of energy as food, 5 g of fat or 9 g of carbohydrate? (c) The metabolism of glucose produces CO2(g) and H2O(l). How does the
(a) Why are fats well suited for energy storage in the human body? (b) A particular chip snack food is composed of 12% protein, 14% fat, and the rest carbohydrate. What percentage of the calorie
(a) A serving of a particular ready-to-serve chicken noodle soup contains 2.5 g fat, 14 g carbohydrate, and 7 g protein. Estimate the number of Calories in a serving. (b) According to its nutrition
A pound of plain M&M® candies contains 96 g fat, 320 g carbohydrate, and 21 g protein. What is the fuel value in kJ in a 42-g (about 1.5 oz) serving? How many Calories does it provide?
The heat of combustion of fructose, C6H12O6, is -2812 kJ/mol. If a fresh golden delicious apple weighing 4.23 oz (120 g) contains 16.0 g of fructose, what caloric content does the fructose contribute
The heat of combustion of ethanol, C2H5OH(l), is -1367 kJ/mol. A batch of Sauvignon Blanc wine contains 10.6% ethanol by mass. Assuming the density of the wine to be 1.0 g/mL, what is the caloric
The standard enthalpies of formation of gaseous propyne (C3H4), propylene (C3H6), and propane (C3H8) are + 185.4, +20.4, and -103.8 kJ/mol, respectively. (a) Calculate the heat evolved per mole on
It is interesting to compare the "fuel value" of a hydrocarbon in a world where fluorine rather than oxygen is the combustion agent. The enthalpy of formation of CF4(g) is -679.9 kJ/mol. Which of the
At the end of 2009, global population was about 6.8 billion people. What mass of glucose in kg would be needed to provide 1500 Cal/person/day of nourishment to the global population for one year?
Imagine a container placed in a tub of water, as depicted in the accompanying diagram.(a) If the contents of the container are the system and heat is able to flow through the container walls, what
The automobile fuel called E85 consists of 85% ethanol and 15% gasoline. E85 can be used in so-called "flex-fuel" vehicles (FFVs), which can use gasoline, ethanol, or a mix as fuels. Assume that
At 20°C (approximately room temperature) the average velocity of N2 molecules in air is 1050 mph. (a) What is the average speed in m/s? (b) What is the kinetic energy (in J) of an N2 molecule moving
Suppose an Olympic diver who weighs 52.0 kg executes a straight dive from a 10-m platform. At the apex of the dive, the diver is 10.8 m above the surface of the water. (a) What is the potential
The air bags that provide protection in autos in the event of an accident expand because of a rapid chemical reaction. From the viewpoint of the chemical reactants as the system, what do you expect
An aluminum can of a soft drink is placed in a freezer. Later, you find that the can is split open and its contents frozen. Work was done on the can in splitting it open. Where did the energy for
Consider a system consisting of the following apparatus, in which gas is confined in one flask and there is a vacuum in the other flask. The flasks are separated by a valve that, when opened,
A sample of gas is contained in a cylinder-and-piston arrangement. It undergoes the change in state shown in the drawing.(a) Assume first that the cylinder and piston are perfect thermal insulators
Consider the systems shown in Figure 5.10. In one case the battery becomes completely discharged by running the current through a heater and in the other case by running a fan. Both processes occur
A house is designed to have passive solar energy features. Brickwork incorporated into the interior of the house acts as a heat absorber. Each brick weighs approximately 1.8 kg. The specific heat of
Mars has an average atmospheric pressure of 0.007 atm. would it be easier or harder to drink from a straw on Mars than on Earth? Explain.
Consider the following samples of gases:If the three samples are all at the same temperature, rank them with respect to (a) Total pressure, (b) Partial pressure of helium, (c) Density, (d) Average
Table 10.3 shows that the van der Waals b parameter has units of L/mol. This means that we can calculate the sizes of atoms or molecules from the b parameter. Refer back to the discussion in Section
A 15.0-L tank is filled with helium gas at a pressure of 1.00 x 102 atm. How many balloons (each 2.00 L) can be inflated to a pressure of 1.00 atm, assuming that the temperature remains constant and
To minimize the rate of evaporation of the tungsten filament, 1.4 x 10-5 mol of argon is placed in a 600-cm3 light bulb. What is the pressure of argon in the light bulb at 23oC?
Carbon dioxide, which is recognized as the major contributor to global warming as a "greenhouse gas," is formed when fossil fuels are combusted, as in electrical power plants fueled by coal, oil, or
Propane, C3H8, liquefies under modest pressure, allowing a large amount to be stored in a container. (a) Calculate the number of moles of propane gas in a 110-L container at 3.00 atm and 27oC. (b)
Nickel carbonyl, Ni (CO)4, is one of the most toxic substances known. The present maximum allowable concentration in laboratory air during an 8-hr workday is 1 ppb (parts per billion) by volume,
When a large evacuated flask is filled with argon gas, its mass increases by 3.224 g when the same flask is again evacuated and then filled with a gas of unknown molar mass, the mass increase is
Consider the arrangement of bulbs shown in the drawing. Each of the bulbs contains a gas at the pressure shown. What is the pressure of the system when all the stopcocks are opened, assuming that the
Assume that a single cylinder of an automobile engine has a volume of 524cm3. (a) If the cylinder is full of air at 74oC and 0.980 atm, how many moles of O2 are present? (The mole fraction of O2 in
A thin glass tube 1 m long is filled with Ar gas at 1 atm, and the ends are stoppered with cotton plugs:HCl gas is introduced at one end of the tube, and simultaneously NH3 gas is introduced at the
Assume that an exhaled breath of air consists of 74.8% N2, 15.3% O2, 3.7% CO2 and 6.2% water vapor. (a) If the total pressure of the gases is 0.985 atm, calculate the partial pressure of each
A 1.42-g sample of helium and an unknown mass of O2 are mixed in a flask at room temperature. The partial pressure of the helium is 42.5 torr, and that of the oxygen is 158 torr. What is the mass of
A gaseous mixture of O2 and Kr has a density of 1.104 g/L at 355 torr and 400 K.What is the mole percent O2 in the mixture?
The density of a gas of unknown molar mass was measured as a function of pressure at 0oC, as in the table that follows.(a) Determine a precise molar mass for the gas.(b)Why is d/P not a constant as a
A glass vessel fitted with a stopcock valve has a mass of 337.428 g when evacuated. When filled with Ar, it has a mass of 339.854 g. When evacuated and refilled with a mixture of Ne and Ar, under the
You have a sample of gas at -33oC. You wish to increase the rms speed by a factor of 2. To what temperature should the gas be heated?
Consider the following gases, all at STP: Ne, SF6, N2, CH4. (a) Which gas is most likely to depart from the assumption of the kinetic-molecular theory that says there are no attractive or repulsive
Does the effect of intermolecular attraction on the properties of a gas become more significant or less significant if? (a) The gas is compressed to a smaller volume at constant temperature; (b) The
Which of the noble gases other than radon would you expect to depart most readily from ideal behavior? Use the density data in Table 7.8 to show evidence in support of your answer.
It turns out that the van der Waals constant b equals four times the total volume actually occupied by the molecules of a mole of gas. Using this figure, calculate the fraction of the volume in a
Which substances in Table 10.3 would you expect to deviate most from ideal-gas behavior at low temperature and high pressure? Which would deviate least? Explain.
Large amounts of nitrogen gas are used in the manufacture of ammonia, principally for use in fertilizers. Suppose 120.00 kg of N2 (g) is stored in a 1100.0-L metal cylinder at 280oC.(a) Calculate the
Cyclopropane, a gas used with oxygen as a general anesthetic, is composed of 85.7% and 14.3% by mass. (a) If 1.56 g of cyclopropane has a volume of 1.00 L at 0.984 atm and 50.0oC, what is the
Consider the combustion reaction between 25.0 mL of liquid methanol (Density = 0.850 g/ml) and 12.5 L of oxygen gas measured at STP. The products of the reaction are CO2 (g) and H2O (g). Calculate
An herbicide is found to contain only C, H, N, and Cl. The complete combustion of a 100.0-mg sample of the herbicide in excess oxygen produces 83.16 mL of CO2 and 73.30 mL of H2O vapor at STP. A
A 4.00-g sample of a mixture of CaO and BaO is placed in a 1.00-L vessel containing CO2 gas at a pressure of 730 torr and a temperature of 25oC. The CO2 reacts with the CaO and BaO, forming CaCO3 and
Ammonia and hydrogen chloride react to form solid ammonium chloride:NH3 (g) + HCl (g) †’ NH4CL (s)Two 2.00-L flasks at 25oC are connected by a valve, as shown in the drawing on the next
The "Chemistry Put to Work" box on pipelines in Section 10.5 mentions that the total deliverability of natural gas (methane, CH4) to the various regions of the United States is on the order 2.7 x

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