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A fuel is burned in a cylinder equipped with a piston. The initial volume of the cylinder is 0.250 L, and the final volume is 0.980 L. If the piston expands against a constant pressure of 1.35 atm, how much work (in J) is done? 11 L@atm = 101.3 J2

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-99.8 J

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Chemistry - Marcador

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-99.8 J

Gases A(g) and B(g) are confined in a cylinder-and-piston arrangement like that in Figure 5.4 and react to form a solid product C(s): A1g2 + B1g2 ¡ C1s2. As the reaction occurs, the system loses 1150 J of heat to the surroundings. The piston moves downward as the gases react to form a solid. As the volume of the gas decreases under the constant pressure of the atmosphere, the surroundings do 480 J of work on the system. What is the change in the internal energy of the system?

-670 J

Indicate the sign of the enthalpy change, ∆H, in the following processes carried out under atmospheric pressure and indicate whether each process is endothermic or exothermic: (a) An ice cube melts; (b) 1 g of butane 1C4H102 is combusted in sufficient oxygen to give complete combustion to CO2 and H2O.

∆H is negative

In (a) the water that makes up the ice cube is the system. The ice cube absorbs heat from the surroundings as it melts, so ∆H is positive and the process is endothermic. In (b) the system is the 1 g of butane and the oxygen required to combust it. The combustion of butane in oxygen gives off heat, so ∆H is negative and the process is exothermic.

How much heat is released when 4.50 g of methane gas is burned in a constant-pressure system? (Use the information given in Equation 5.17.)

-250 kJ

Given reaction N2 + 3H2  2NH3, you mix 1 mol each of nitrogen and hydrogen gases under the same conditions in a container fitted with a piston. Calculate the ratio of volumes of the container (Vfinal/Vinitial). A) 0.67 B) 1.00 C) 1.33 D) 1.50 E) none of these

As indicated by Lewis structures, which of the following species could probably not exist as a stable molecule? A) NH3 B) N2H2 C) N2H4 D) N2H6 E) N2O4

ANS: D PTS: 1 DIF: Moderate REF: 8.11 KEY: Chemistry | general chemistry | bonding | covalent bonding | exceptions to the octet rule

Which item (a, b or c) in each of the three groups below has the lowest entropy? I. (a) 10 g ice (b) 10 g water vapor (c) 10 g liquid water II. (a) 1 mole NaCl solid (b) 1 mol NaCl in 1 M aqueous solution (c) 1 mol molten NaCl III. (a) 1 mole C2H6(g), (b) 1 mole CH4(g), (c) 1 mol C3H8(g) all at 25 C and 1 atm A) a, a, b B) c, b, c C) b, b, c D) a, b, c E) a, a, c

A 0.186 M solution of the salt NaA has a pH of 8.40. Calculate the Ka value of the acid HA. A) 3.4*10–11 B) 7.4 *10–10 C) 2.9 *10–4 D) 1.2 *102 E) none of these

ANS: C PTS: 1 DIF: Moderate REF: 14.8 KEY: Chemistry | general chemistry | acids and bases | solutions of a weak acid or base | acid-base properties of salt solutions MSC: Quantitative

What is the hybridization of the carbon atom that is double-bonded to oxygen? A) sp B) sp2 C) sp3 D) dsp3 E) d2sp3

ANS: B PTS: 1 DIF: Easy REF: 9.1 KEY: Chemistry | general chemistry | bonding | bonding theories | hybridization MSC: Conceptual

A substance, A2B, has the composition by mass of 60% A and 40% B. What is the composition of AB2 by mass? A) 40% A, 60% B B) 50% A, 50% B C) 27% A, 73% B D) 33% A, 67% B E) none of these

ANS: C Use an arbitrary mass, 100 g is an easy number to work with. 60% of 100 g is 60 g, there are two A's. Each A is 30 g 40 g is B, and there is only one, so B is 40 g. AB2, would have a mass of 30 g + 2*40 g = 110 g The new percent by mass composition of A is: 30g110g∗100%=27.3% The new percent by mass composition of B is: 80g110g∗100%=72.7%

Indium reacts with chlorine to form InCl3. In the balanced equation for this reaction, the coefficient of the indium trichloride is A) 1 B) 2 C) 3 D) 4 E) 6

B 2In + 3Cl2 → 2InCl3

You heat 3.869 g of a mixture of Fe3O4 and FeO to form 4.141 g Fe2O3. The mass of oxygen reacted is A) 0.272 g B) 0.476 g C) 1.242 g D) 1.000 g E) none of these

A Your original mixture contains iron(II, III) oxide, Fe3O4, and iron(II) oxide, FeO, in some unknown proportion. After you heat this mixture, it will react with the oxygen in the air to produce iron(III) oxide, Fe2O3. Notice that the mass of the mixture increases from 3.869 g to 4.141 g. So what causes this increase in mass? The amount of oxygen the react with the initial mixture to form the iron(III) oxide! This means that the mass of oxygen that reacted will be equal to the difference between the final mass and the initial mass of the mixture mFe2O3=mmixture+moxygen moxygen=mFe2O3−mmixture moxygen=4.141 g−3.869 g=0.272 g https://socratic.org/questions/5612eb9f581e2a39ce51b7c6

23. An analytical procedure requires a solution of chloride ions. How many grams of NaCl must be dissolved to make 1.95 L of 0.0561 M Cl–? A) 3.28 g B) 0.595 g C) 6.39 g D) 1.64 g E) 12.8 g

ANS: C PTS: 1 DIF: Moderate REF: 4.3 KEY: Chemistry | general chemistry | chemical reactions | working with solutions | concentration

36. An ion is formed A) By either adding or subtracting protons from the atom. B) By either adding or subtracting electrons from the atom C) By either adding or subtracting neutrons from the atom. D) All of the above are true. E) Two of the above are true.

29. Which of the following favors the solubility of an ionic solid in a liquid solvent? A) a large magnitude of the solvation energy of the ions B) a small magnitude of the lattice energy of the solute C) a large polarity of the solvent D) all of the above E) none of the above

14. Which of the following is true for a buffered solution? A) The solution resists change in its [H+]. B) The solution will not change its pH very much even if a concentrated acid is added. C) The solution will not change its pH very much even if a strong base is added. D) Any H+ ions will react with a conjugate base of a weak acid already in solution. E) All of these.

ANS: E PTS: 1 DIF: Easy REF: 15.2 KEY: Chemistry | general chemistry | acids and bases | solutions of a weak acid or base with another solute | buffer

19. You have a certain mass of helium gas (He) in a rigid steel container. You add the same mass of neon gas (Ne) to this container. Which of the following best describes what happens? Assume the temperature is constant. A) The pressure in the container doubles. B) The pressure in the container increases but does not double. C) The pressure in the container more than doubles. D) The volume of the container doubles. E) The volume of the container more than doubles.

In the hydrogen spectrum, what is the wavelength of light associated with the n = 3 to n = 1 electron transition? A) 3.97 * 10^–25 nm B) 8.21 *10^2 nm C) 9.75 *10^6 cm D) 1.94 * 10^–18 m E) 1.03 *10^–7 m

Which of the following arrangements is in order of increasing size? A) Ga3+ > Ca2+ > K+ > Cl– > S2– B) S2– > Cl– > K+ > Ca2+ > Ga3+ C) Ga3+ > S2– > Ca2+ > Cl– > K+ D) Ga3+ > Ca2+ > S2– > Cl– > K+ E) Ga3+ > Ca2+ > S2– > K+ > Cl–

A PTS: 1 DIF: Moderate REF: 8.4 KEY: Chemistry | general chemistry | bonding | ionic bonding | ionic radii

97. Which of these statements is a consequence (follows from) the Law of Definite Proportion? A) All samples of chlorine contain 35Cl and 37Cl in the same (definite) ratio. B) The mass of oxygen that is combined with a fixed mass of nitrogen in each of the binary nitrogen oxides can be expressed as a ratio of small whole numbers. C) The atomic masses of all of the elements in the periodic table have fixed values. D) The % lead by mass in the compound galena is the same for all pure samples obtained from any source. E) None of these is correct

D PTS: 1 DIF: Easy REF: 2.2 KEY: Chemistry | general chemistry | early atomic theory | atomic theory of matter | Dalton's atomic theory

Given that Ka for HOCl is 3.5 * 10^–8 and the Ka for HF is 7.2 * 10^–4 (both at 25°C), which of the following is true concerning K for the above reaction at 25°C? A) K is greater than 1. B) K is less than 1. C) K is equal to 1. D) Cannot be determined with the above information. E) None of these (A-D).

B PTS: 1 DIF: Moderate REF: 14.2 KEY: Chemistry | general chemistry | chemical equilibrium | equilibrium constant |

Consider a solution consisting of the following two buffer systems: H2CO3 HCO3– + H+ pKa = 6.4 H2PO4– HPO42– + H+ pKa = 7.2 At pH 6.4, which one of the following is true of the relative amounts of acid and conjugate base present? A) [H2CO3] > [HCO3–] and [H2PO4–] > [HPO42–] B) [H2CO3] = [HCO3–] and [H2PO4–] > [HPO42–] C) [H2CO3] = [HCO3–] and [HPO42–] > [H2PO4–] D) [HCO3–] > [H2CO3] and [HPO42–] > [H2PO4–] E) [H2CO3] > [HCO3–] and [HPO42–] > [H2PO4–]

A 20.0-g sample of methyl alcohol (CH3OH, molar mass = 32.04 g/mol) was dissolved in 43.3 g of water. The mole fraction of CH3OH is: A) 0.260 B) 0.624 C) 0.316 D) 4.85 E) 0.206

ANS: E PTS: 1 DIF: Easy REF: 11.1 KEY: Chemistry | general chemistry | solutions | expressing concentration | mole fraction MSC: Quantitative

The solubility of silver phosphate, Ag3PO4, at 25°C is 1.55*10–5 mol/L. Determine the concentration of the Ag+ ion in a saturated solution. A) 1.55 * 10^-5 M B) 5.17 *10^-6 M C) 4.65 *10^-5 M D) 1.94 * 10^5 M E) 3.72 * 10^-15 M

ANS: C PTS: 1 DIF: Easy REF: 16.1 KEY: Chemistry | general chemistry | solubility | solubility equilibria | solubility product constant

A solution contains 0.500 M HA (Ka = 1.0  10–8) and 0.432 M NaA. What is the [H+] after 0.10 mole of HCl is added to 1.00 L of this solution? A) 1.0 *10^–8 M B) 3.0 * 10^–8 M C) 5.5 * 10^21 M D) 1.8 * 10^–8 M E) none of these

Determine the initial rate of B consumption ([B]/t) for the first trial? A) 8.00  10–3 mol/L·s B) 1.60  10–2 mol/L·s C) 3.20  10–2 mol/L·s D) 4.00  10–3 mol/L·s E) none of these (A-D)

ANS: B PTS: 1 DIF: Moderate REF: 12.3 KEY: Chemistry | general chemistry | rates of reaction | reaction rate | change of concentration with time

In which single flask do the molecules have the greatest mass, the greatest average velocity, and the highest kinetic energy? A) Flask A B) Flask B C) Flask C D) All are the same. E) No one flask has all these.

ANS: E PTS: 1 DIF: Moderate REF: 5.6 KEY: Chemistry | general chemistry | phases | gas | kinetic-molecular theory MSC: Conceptual

We generally report a measurement by recording all of the certain digits plus ____ uncertain digit(s). A) no B) one C) two D) three E) four

ANS: B DIF: Easy REF: 1.5 KEY: Chemistry | general chemistry | general concepts | measurement | significant figures MSC: Conceptual

Body temperature is about 309 K. On a cold day, what volume of air at 276 K must a person with a lung capacity of 2.2 L breathe in to fill the lungs? A) 2.46 L B) 1.97 L C) 2.08 L D) 3.93 L E) none of these

A general reaction written as A + 2B  C + 2D is studied and yields the following data: [A]0 [B]0 Initial [C]/t 0.150 M 0.150 M 8.00 * 10^–3 mol/L·s 0.150 M 0.300 M 1.60 * 10^–2 mol/L·s 0.300 M 0.150 M 3.20 * 10^–2 mol/L·s 13. What is the order of the reaction with respect to B? A) 0 B) 1 C) 2 D) 3 E) 4

You have solutions of 0.200 M HNO2 and 0.200 M KNO2 (Ka for HNO2 = 4.00 * 10^–4). A buffer of pH 3.000 is needed. What volumes of HNO2 and KNO2 are required to make 1 liter of buffered solution? A) 500 mL of each B) 286 mL HNO2; 714 mL KNO2 C) 413 mL HNO2; 587 mL KNO2 D) 714 mL HNO2; 286 mL KNO2 E) 587 mL HNO2; 413 mL KNO2

How many electrons are transferred in the following reaction? 2ClO3– + 12H+ + 10I–  5I2 + Cl2 + 6H2O A) 12 B) 5 C) 2 D) 30 E) 10

ANS: E PTS: 1 DIF: Easy REF: 18.1 KEY: Chemistry | general chemistry | electrochemistry | half-reaction | balancing chemical equation