Energetics Questions and Answers

A mole of helium in the process of expansion has constant molar heat capacity during the process which is equal to C = 15 J/ (mol - K). The gas does 20 J work during the process. Take R = 25/3 J/mol K The heat given to the gas is 120 J The temperature of the gas increases by 8 K Heat extracted from the gas is 80 J The pressure of the gas increases during the process.

A bomb calorimeter has a heat capacity of 2.47 kJ/K. When a 3.74x10^-3 mol sample of ethylene was burned in this calorimeter, the temperature increased by 2.14 K. Calculate the energy of combustion for one mole of ethylene.

For a phase change, ΔH = 31 kJ/mol and ΔSº = 0.093 kJ/(K-mol). What are ΔG and the spontaneity of the phase change at 300 K? A. ΔG= 3.1 kJ; nonspontaneous B. ΔG= 3.1 kJ; spontaneous C. ΔG-59 kJ; nonspontaneous D. ΔG= 59 kJ; spontaneous

Suppose 140 kJ energy is required to do a certain task by a man. How much amount of glucose (in gram) has to be consumed by man to do the work, if only 50% energy is available for muscular work? [Heat of combustion of glucose is -2800 kJ/mol in human body]

The heat of fusion ΔHf, of benzene (C6H6) is 10.6 kJ/mol. Calculate the change in entropy ΔS when 256. g of benzene freezes at 5.6 °C. Be sure your answer contains a unit symbol and the correct number of significant digits.

Which of the following sequences is correct about the excitation of an atom? Atoms in the excited state - atom emits energy - one or more electrons move to the higher level One or more electrons move to the higher level - atoms in the excited state - atom absorbs energy Atoms in ground state - atom absorbs energy - one or more electrons move to the higher level One or more electrons move to the higher level - atoms in ground state - atom absorbs energy

A student's thermometer reads 102.2°C when placed in boiling water. The student then used the same thermometer to test the temperature of a solution, and the thermometer read 89.0°C. What value should the student write down as the actual temperature of the solution?

The following equilibrium exists at 1000 °C with Kc = 2.00. 2 COF2 (g) CO2 (g) + CF4 (g) If a 5.00-L mixture contains 0.145 mol COF2, 0.262 mol of CO2 and 0.074 mol of CF4 at 1000 °C, in which direction will the mixture proceed to reach equilibrium?

The lead-acid storage battery is the oldest rechargeable battery in existence. It was invented in 1859 by French physician Gaston Plante and still retains application today, more than 150 years later. There are two reactions that take place during discharge of the lead-acid storage battery. In one step, sulfuric acid decomposes to form sulfur trioxide and water: H₂SO4(l)→ SO3(g) + H₂O(l) ΔH=-775. kJ In another step, lead, lead(IV) oxide, and sulfur trioxide react to form lead(II) sulfate: Pb(s) + PbO₂(s) + 2 SO 3(g) - 2 PbSO4(s) ΔH=+113. kJ Calculate the net change in enthalpy for the formation of one mole of lead (II) sulfate from lead, lead(IV) oxide, and sulfuric acid from these reactions. Round your answer to the nearest kJ.

The value of AG at 25 °C for the formation of POC13 from its constituent elements, P2 (g) + O2 (g) + 3Cl2 (g) - 2POC13 (g) A)-1108.7 B) +606.2 C) +1108.7 D) -1,005 E) -606.2

What is the boiling point of water in a pressure cooker with a pressure of 2.00 atm? The enthalpy of vaporization of water is 40.7 kJ/mol (R = 8.314 J/mol*K). 81 oC 141 oC 157 OC 101 oC 121 oC

Which of the following indicates what happens if methane, CH4, freezes at 25 °C? Its melting point is-182 °C and its boiling point is -161 °C. Free energy increases, entropy increases, and enthalpy increases. Free energy decreases, entropy increases, and enthalpy decreases. Free energy decreases, entropy decreases, and enthalpy increases. Free energy increases, entropy decreases, and enthalpy decreases. Free energy decreases, entropy decreases, and enthalpy decreases.

A cold aluminum can of soda is placed outside on a hot 35°C day. Droplets of water with a mass of 24.3 grams form on the outside of the can. Which of these would be appropriate to calculate the energy that left the water as it formed liquid droplets on the outside of the can. Select one: heat of fusion of water heat of vaporization of aluminum specific heat capacity of aluminum heat of vaporization of water specific heat capacity of water

Given the data below, use Hess's law to calculate ΔH for the reaction: N₂O(g) + NO2(g) → 3 NO(g) 2 N₂O(g) → 2 N2(g) + O2(g) 2 NO(g) + O2(g) → 2 NO2(g) N2(g) + O2(g) → 2 NO(g) ΔH-163.2 kJ ΔH-113.1 kJ ΔH = +180.7 kJ

A chemical engineer must calculate the maximum safe operating temperature of a high-pressure gas reaction vessel. The vessel is a stainless-steel cylinder that measures 37.0 cm wide and 44.4 cm high. The maximum safe pressure inside the vessel has been measured to be 1.00 MPa. For a certain reaction the vessel may contain up to 0.614 kg of boron trifluoride gas. Calculate the maximum safe operating temperature the engineer should recommend for this reaction. Write your answer in degrees Celsius. Round your answer to 3 significant digits.

According to Thomas Paine in his essay "Common Sense, "What, if delayed longer, will be harder to accomplish? Overthrowing the government Independence of America Establishing a republic Reconciliation

A 44.0 g sample of an alloy is heated to 106.0 °C and dropped into 83.6 g of water at 22.0 °C. The final temperature is 38.0 °C. The specific heat of water is 4.184 J.g¹.C. What is the specific heat of the alloy? 7.95 J-g-¹.°C-1 0.447 J-g-¹.°C-1 0.535 J-g-¹.°C¯l 1.87 J.g¯¹.°C-¹

A 100.0 mL room temperature sample of 0.500 M NaOH is mixed with a room temperature 100.0 mL sample of 0.500 M HNO3 in a "coffee cup" calorimeter. The initial temperature was 21.7 °C and the final temperature after the reaction completed was measured to be 25.1 °C. The chemical reaction is given below: HNO3(aq) + NaOH(aq) ➜ NaNO3(aq) + H2O (l) Assume that the density of all the solutions is 1.000 g/mL and that the specific heat of all the solutions is 4.184 J/g°C. What is the amount of heat gained by the solution? Round answer to 4 significant figures.

N₂H4(l) + O₂(g) → 2 H₂O(l) + N₂(g) C8H16(g) + H₂(g) → CgH18(g) H₂O(l) → H₂O(g) 2 CH₂OH()→2 CH4(g) + O₂(g) 2 NO(g) + Cl₂(g) → 2 NOCI(g) Consider the simple case of the vaporization of water, the third reaction listed. Experience tells us that (at 1 atm) liquid water will boil at temperatures above 373 K but water vapor will condense, the opposite reaction, at lower temperatures. What is the value of AS universe at 300 K, in units of J K-¹ mol-¹?

Carbon monoxide (CO) is toxic because it binds more strongly to the iron in hemoglobin (Hb) than does oxygen (O₂), as indicated by these approximate standard free-energy changes in blood: reaction A: Hb + 0₂ Estimate the equilibrium constant K at 298 K for the equilibrium K= Express your answer numerically using one significant figure. reaction B: Hb+CO HbCO, AG = -80 kJ/mol →→HbO₂, ? AG=-70 kJ/mol HbO, +CO , HbCO+O2

Calculate the formation constant for the formation of [Cu(NH3)2 (H₂O)4]2+ from [Cu(H₂O)6]2+, given that AG is -44.7 kJ mol-1 at 298 K. Express your answer numerically to three significant figures.

10.1 g CaO is dropped into a styrofoam coffee cup containing 157 g H2O at 18.0°C. If the following reaction occurs, then what temperature will the water reach, assuming that the cup is a perfect insulator and that the cup absorbs only a negligible amount of heat? [specific heat of water = 4.18 J/g °C] CaO(s) + H₂O(l)→ Ca(OH)₂(s) = -64.8 kJ/mol A. 18.02°C B. 117°C C. 35.8°C D. 42.2°C E. 311°C

Given the following equation: 2 Al(s) +3/2 O2(g) → Al2O3(s) AH = -2,251 kJ Calculate the AH for the following reaction: 2 Al2O3(s)→ 4 Al(s) + 3 O₂(g)

Propane, C3Hg, reacts with oxygen to produce carbon dioxide, water and heat. C3H8 +5O2 3 CO₂ + 4H₂O AH = -2,002.1 kJ/mol What is of heat(q) released if 11.7 g of O₂ are consumed in the reaction?

8) Calculate the standard enthalpy change for the reaction 2C8H18(l)+ 17O2(g) → 16CO(g) + 18H₂O(l). Given: 2C8H18(l) +25O2(g) → 16CO₂(g) + 18H₂O(l) AH = -11,020 kJ/mol 2CO(g) + O₂(g) → 2CO2(g) AH-566.0 kJ/mol A) 15,550 kJ/mol B) -6,492 kJ/mol C) 10,450 kJ/mol D) -10.450 kJ/mol E) 6,492 kJ/mol

Using Table 7.2 and 7.3 from Section 7.5 of the OpenStax textbook entitled Chemistry 2E by Flowers, Leopold et al. what is the enthalpy change, AH for the decomposition of hydrogen iodide 2 HI→ I₂ + H₂

A "cool" Bunsen burner flame is used to heat substances in a test tube because... it will heat the substance better. it will waiver in the air less than a hot flame. all of these choices are valid. it will be less likely to crack the test tube.

Hydrogen gas reacts with oxygen to form water. 2 H₂ (g) + O₂ (g) ® 2 H₂O (g) DH = ??? In one experiment 1.888 g of hydrogen react to form 226.4 kJ of heat. Based on this information, calculate the enthalpy for the reaction as written above. -241.7 kJ +241.7 kJ -483.5 kJ -212.0 kJ

In this experiment, the following reaction enthalpies were determine: 1) NaOH(s) - NaOH(aq) AH = -41 kJ 2) NaOH(s) + HCl(aq) -NaCl(aq) + H₂O(1) AH = -108.9 kJ Use Hess's law to determine the reaction enthalpy of 3) NaOH(aq) + HCl(aq) -NaCl(aq) + H₂O(1) AH = ? kJ (Answer to 1 decimalplace)

A 6000. L storage tank initially was filled with 850. kPa of methane gas, maintained at 20.0°C is located by a small power plant. The power plant draws in 500. L of water for a day at 15.0 °C from the lake. This amount of water is then being heated to a superheated steam at 200°C to power the turbine that is used to generate electricity. A. Calculate the heat required to bring the 500. L of water from 15.0 °C to 200.°C B. Calculate the heat generated by the combustion of the methane gas. C. Determine the final pressure of the methane gas at in the storage tank at the end of the day.

Which situation has the greatest amount of potential energy? A golf ball sitting on the same table. A bowling ball sitting on a table. A golf ball sitting on the floor. A bowling ball sitting on the floor.

How much energy must be removed from a 125 g sample of benzene (molar mass= 78.11 g/mol) at 425.0 K to liquify the sample and lower the temperature to 335.0 K? AHvap = 33.9 kJ/mol AHfus = 9.8 kJ/mol Cliq= =1.73 J/g °C Cgas = 1.06 J/g°C Csol = 1.51 J/g°C Tmelting =279.0 K Tboiling = 353.0 K A) 38.9 kJ B) 95.4 kJ C) 67.7 kJ D) 54.3 kJ E) 74.4 kJ

Use standard enthalpies of formation to determine the AHO in kJ for the following reaction: 4NH3(g) +5O2(g) → 4NO(g) + 6H2O(g) AH (NH3(g)) = -45.90 kJ/mol AH (NO(g)) = 90.29 kJ/mol AH(H2O(g)) = -241.83 kJ/mol

A student adds 15.0 g of LiBr(s) to an insulated container holding 150.0 g of water at 22.0°C. After the LiBr(s) has completely dissolved, the final temperature of the solution is 34.2°C. Calculate the amount of heat, in kJ, that was absorbed by the solution during the dissolution process. (Assume that the solution has a specific heat of 4.18 J/(g. °C).) Write your answer using three significant figures.

Given the enthalpy of reaction (AH°) for the reaction shown below, what is AE° for this reaction? (Hints: what is the work in this reaction caused by? Symbol denotes standard thermodynamic conditions: 25 °C and 1 atm) HCl(aq) +CaCO3 (s)→ CaCl2 (aq) + H₂O (1) + CO₂ (g) AH = -350.0 kJ

A cylinder with a moving piston expands from an initial volume of 0.250 L against an external pressure of 2.00 atm. The expansion does 288 J of work on the surroundings. What is the final volume of the cylinder?

The standard heat of reaction (AH°) for the reaction shown below is -1985 kJ. Based on the AH°f given for each substance, determine the AH°f for C3H8O.

Using the equations 2 Fe (s) + 3 Cl₂ (g) → 2 FeCl3 (s) AH = -800.0 kJ/mol Si(s) + 2 Cl: (g) → SiCl4 (s) AH = -640.1 kJ/mol Determine the molar enthalpy (in kJ/mol) for the reaction 3 SiCl (s) + 4 Fe (s)→ 4 FeCl3 (s) + 3 Si (s)

A fuel was used to heat water in a calorimetry experiment. Sucrose was burnt causing a temperature change of 14.4 K in1250 g of water (specific heat capacity = 4.18 J/g.K). Calculate the heat change of the water. Heat change (J) = mass (g) x specific heat capacity (J/g K) x temperature change (K)