Energetics Questions and Answers

Given the information below, what is the change in enthalpy (in kJ) when 1.32 x 105 kg of liquid H₂ is burned? 2 H₂ (/)+02 (1)→ 2 H₂O (/) ΔH'rxn=-571.6 kJ a-3.74 x 1010 b.-285.8 Oc-571.6 d.-1.87 x 1010

How much heat, in Jouls, is required to raise the temperature of 213.9 g of a hydrocarbon from 38.7 °C to 92.5 °C if the specific heat of the hydrocarbon is 1.73 J/g °C? Provide answer to 3 significant figures and use the abbreviation of the unit. Do not use scientific notation.

The combustion of glucose, C6H12O6 (s), produces carbon dioxide, CO2 (g), and water, H₂O(g), according to the equation below. C6H12O6 (s) +60₂(g) → 6CO₂(g) + 6H₂O(l) The enthalpy of the reaction is -2,840 kJ. What is the heat of combustion, per mole, of glucose? -2,840 kJ/mol -473.3 kJ/mol 473.3 kJ/mol 2,840 kJ/mol

What is the energy change when the temperature of 11.0 grams of solid zinc is decreased from 39.2 °C to 23.6 °C ? Answer: Joules.

A scientist measures the standard enthalpy change for the following reaction to be -173.9 kJ: HCl(g) + NH3(g) ⇒ NH4Cl(s) Based on this value and the standard enthalpies of formation for the other substances, the standard enthalpy of formation of NH3(g) is kJ/mol.

A sample of methane gas (CH4) with mass 0.320 g is burned and heats a sample of water of mass 200.0 g. The temperature of the water rises from 20.0°C to 27.2°C. Assuming all of the heat is transferred to the water find the molar heat of combustion of methane.

10. A chemical reaction occurs in 350.0 grams of water and raises water's temperature from 21.5°C to 56.3°C. a) How much heat is involved? b) Did the water gain or lose heat? c) Did the reaction absorb or release heat? d) Was the reaction endothermic or exothermic? Explain.

8. If 1.50 x 10³ grams of mercury loses 3.50 kJ of heat, how much does the temperature drop? If the original temperature was 90.0°C, what is the final temperature? (Cp = 0.14 J/g°C, for mercury)

In a chemical equation, the sum of the masses of the products is less than the reactants of the products is more than the reactants of the products is equal to the reactants of the products is not equal to the reactants

The heat required to raise the temperature of the unit mass of a given substance by a given amount (usually one degree). Molarity Specific Heat Density Dilution

Calculate AH for the following reaction. C6H6(1) + O2(g) → C(s) + H₂0 (l) State whether the reaction is exothermic or endothermic and why. The molar enthalpies of combustion of carbon, hydrogen gas, and benzene, are -394 kJ/mol, -286 kJ/mol, and -3,267.4 kJ/mol, respectively. [4A,2T]

Q = mx cx (change in temperature) Calculate the heat capacity of a piece of wood if 1500.0 grams of the wood absorbs 6.75 x 104 Joules of heat and its temperature changes from 32 to 57 degrees celsius? 0.12 J/gºC 55.4 J/gºC 1.8 J/gºC 13.2 J/gºC

Q = mx cx (change in temperature) 100 ml of 4.0° C water is heated until its temperature is 37° C. If the specific heat of water is 4.18 J/gºC,calculate how much heat you had to have added. 100 J 8,412 J 10,320 J 13,794 J

For the reaction 2SO2 + 02 - 2SO3, AH = -198 kJ. What would the change in enthalpy be for 1 mole of SO3 if the pressure and temperature remain constant? Enter your answer in the box. Use the keys under the box as needed to enter your answer. kJ

A chemical reaction that releases heat from the surroundings is said to be ___ and has a___ΔH at constant pressure. * Exothermic / positive Exothermic / negative Endothermic / positive Endothermic / negative

A taco contains 8 grams of protein, 9 grams of fat and 13 grams of carbohydrates. The mass of fiber is 3 g. Calculate the nutritional value of the taco in kilocalories (common format), calories (scientific notation) and Joules (scientific notation). The nutritional value of the taco is _ kcal =______ cal = ___ Joules

Answer the following thermochemistry problems. You must show the numeric values in their proper place in the formula used to arrive at an answer. In addition, you must pay attention to sig. figs. and units on your answer. Correct answers with no work shown will receive half-credit. a. The specific heat of an unknown metal was determined by heating 100.00g of the metal from 20 °C to 130.86 °C. The resulting energy gained by the metal was 10,000.00J. What is the specific heat? What metal is it (4pt)? b. 26.50g of aluminum is heated to an initial temperature of 100 °C and placed into 200.00g of room temperature water at 20°C. The specific heat of water is 4.182J/g °C and the specific heat of aluminum is 0.902 J/g °C. What is the final temperature of the metal and water(6pt)?

Which of the following reactions are exothermic? (Select all that apply) * (A) H₂O(1) + SO₃(g) → H₂SO₄(I) △H = -135.5 kJ (B) H₂O(l) → H₂(g) + O₂(g) △H = +285.8 kJ (C) C₆H₁₂O₆ + O₂ → CO₂ + H₂O △H = -686 kJ (D) ATP + H₂O → ADP + P △H = -4852.3 kJ (E) ADP + P → ATP + H₂O △H = +7.3 kJ (1) Reaction 1 (2) Reaction 2 (3) Reaction 3 (4) Reaction 4 (5) Reaction 5

The combustion of glucose, C₆H₁₂O₆ (s), produces carbon dioxide, CO₂ (g), and water, H₂O(g), according to the equation below. C₆H₁₂O₆ (s) +6O₂(g) → 6CO₂(g) + 6H₂O(l)

In each row, pick the compound with the bigger lattice energy. Note: lattice energy is always greater than zero. Which compound has the bigger lattice energy? SrCl2 RbCI MgS BaS LiBr Lil

Using the following equations and Hess's Law, find the enthalpy change of the reaction D₂(g) + E₂(g) --> 2DE(g) Remember to include correct units and to round to the nearest 0.01 D₂(g) + 2E₂(g) --> 2 DE₂(g) △H = 65.10 kJ 2DE(g) + E₂(g) --> 2 DE₂(g) △H = -296.73 kJ

A person fully reacts 25.4g of carbon with excess hydrogen gas. How much energy, in kilojoules, is released by the reaction? (Use a negative number if energy is released and a positive number if energy is added.) (Round to 2 Decimal Places) 4C (s) + 5H₂(g) →C4H10 (g) △H° =-125.6 kl/mol

A person reacts12.55mol of carbon with 36.73mol of hydrogen gas. How much energy is released during the reaction? (Use a negative number if energy is released and a positive number if energy is added.) 4C (s) + 5H₂ (g) →C4H10(g) △H° =-125.6 kJ/mol

The formation of nitrogen trichloride is N₂(g) + 3Cl₂(g) ⇄ 2NC3(g) △H = +232 kJ/mol Which change will increase the concentration of the product? A) adding Ne(g) B) removing nitrogen C) decreasing the temperature D) decreasing the volume of the container

4C (s) + 5H₂ (g) → C₄H₁₀ (g) △H° = -125.6 kJ/mol (1) A line graph representing the energy changes in the reaction. (2) An LOL graph modeling changes in chemical and thermal energy.

Under normal room conditions (standard pressure at about 20°C), water will not boil, so we do not observe H₂O(l) + 40.7 kJ – H₂O(g). At this temperature, the process is because.

How many Joules are required to heat 250.0 grams of liquid water from 0 to 100 C? (A) 100,000 J (B) 199,000 J (C) 240,000 J (D) 76,000 J

Suppose 1.00 g of Ca(OH)₂ solid is poured into 50.0 mL of water. The temperature of water changes from 25.0°C to 26.1°C. Assuming no other heat is lost in this process, determine the heat of solution for Ca(OH)₂(s) in kJ/mol.

Water (2630 g) is heated until it just begins to boil. If the water absorbs 4.91×10⁵ J of heat in the process, what was the initial temperature of the water?

Calculate the heat change in calories for vaporization of 30.0 g of water at 100°C. Express your answer as a positive value using three significant figures and include the appropriate units.

Consider the reaction: Ag⁺(aq) + Cl‾(aq) --> AgCl (s) Given the following table of thermodynamic data, Substance △Hf⁰ (kJ/mol) s⁰(J/mol .K) Ag⁺(aq) 105.90 73.93 Cl‾(aq) -167.2 56.5 AgCl(s) -127.0 96.11 determine the temperature (in ⁰C) above which the reaction is nonspontaneous under standard conditions. a. 1230 b. 150 c. 432 d. 133 e. 1640

For which of these processes is the value of H expected to be positive? 1. The temperature increases when calcium chloride dissolves in water. 2. Steam condenses to liquid water 3. Water boils 4. Dry ice sublimates (goes from solid to gas) 4 only 3 and 4 only 1 only 2 and 3 only

You accidentally touch a hot stove. Select all the true statements. If you are the system, this an exothermic process. If you are the system, this is an endothermic process. It feels hot because the stove is transferring energy to you. You can't tell from the information given which direction the energy is transferring. If the stove is the system, this is an endothermic process. If the stove is the system, this is an exothermic process. It feels hot because the stove is taking energy away from you.

What happens to the average kinetic energy of a gas when the particles of the gas collide against each other at a constant temperature and volume? Explain your answer.

12 kJ of heat is required to raise the temperature of 200.0 g of a substance from 25°C to 45°C. Which of the following corresponds to the specific heat capacity of that substance? 6J/gºC 9j/gºC 3 J/g °C 12 J/gºC

In the reaction H-H→H+H, what describes an average energy change of 436 kJ/mol? (H₂ + 436 kJ/mol → 2H) A. The energy will be required as bonds are being broken. B. The energy will be required as bonds are being formed. C. The energy will be released as bonds are being broken. D. The energy will be released as bonds are being formed.

As the temperature of a sample of water increases --- kinetic energy is unaffected by temperature changes. kinetic energy increases. kinetic energy is equal to 0. kinetic energy decreases.

Calculate the standard free energy change for the following reaction: 3-PG+ATP ---> 1,3-BPG + ADP Given the following standard free energies of hydrolysis: ATP = - 31 kJ/mol 1,3-BPG= 49.6 kJ/mol 18.6 kJ/mol 80.6 kJ/mol -18.6 kJ/mol -80.6 kJ/mol

A 440. g quantity of a certain metal is heated to 100.0 °C. It is immediately thrust into 258 g of water that is initially at 25.0°C. The temperature of the metal-water mixture rises to 36.5 °C. What is the specific heat of the metal? The specific heat capacity of the water is 4.184 J/g. °C.

When an exothermic chemical reaction takes place the energy stored in the chemical bonds is released into the surroundings as heat. Which choice below best describes the energy during this process? A. Chemical kinetic energy is converted into thermal potential energy B. Chemical potential energy is converted into thermal kinetic energy C. Thermal kinetic energy is converted into chemical potential energy D. Thermal potential energy is converted into chemical kinetic energy

How much heat is required to heat the kettle from 23.0 °C to 99.0 °C if it contains 1.25 L of water? (Assume the density of the water is 1.00 g/mL and its specific heat is 4.184 J/g °C.)

The specific heat capacity of lead is 0.130 J/g-K. How much heat is required to raise the temperature of 15.0 g of lead from 22.0 °C to 37.0 °C? A. 29.3 J B. 2.0 J C. -0.13 J D. 5.8 x 10-4 J

A 0.500-g sample of KCl is added to 50.0 g of water in a calorimeter. If the temperature decreases by 1.05 °C, what is the approximate amount of heat involved in the dissolution of the KCl, assuming the heat capacity of the resulting solution is 4.184 1/2 °C?

A 3.00 mol sample of C₂H5OH undergoes the phase transition illustrated in the diagram above. The molar enthalpy of vaporization, AHvap of C₂H5OH is +47.9 kJ/mol. Which of the following best identifies the change in enthalpy in the phase transition shown in the diagram above? +143.7 kJ -173.7 kJ +173.7 kJ -143.7 kJ

If 375 J of heat energy are added to 29.0 g of copper, how much will the temperature change? The specific heat of copper is 0.386 J/g °C. You may want to rearrange the formula, Q = m c AT, so that you are solving for AT. Substitute in your variables and solve. Show any work and put your answer in the box.

Aluminum (Al) metal can be recycled from scrap metal by melting the metal to evaporate impurities. Molar heat capacity of a solid Melting point Heat of fusion 24 J/mol-K 933 K 10.7 kJ/mol Calculate the amount of heat needed to purify 4.50 moles of Al originally at 298 K by melting it.

Dichlorine heptoxide, Cl₂O₁, can be formed according to the reaction below. In a particular experiment, 7.00 moles of Cl₂O7 is formed. Which statement below best describes what occurs? AH = 130 kJ/mol 2Cl₂(g) + 70₂(g) → 2C1₂O7(g) A. 455 kJ of energy is released B. 455 kJ of energy is absorbed C. 37.1 kJ of energy is absorbed D. 37.1 kJ of energy is released

It takes copper metal 7500 J of heat to raise the temperature of 30.0 g of copper from 200°C to 875°C. What is the specific heat capacity of copper? a 19x 108 J/g C b. 12.5 J/g C c. 0.38 Jig C d. 4.18 J/gºC

Bond enthalpy is A) always positive B) always negative C) sometimes positive, sometimes negative D) always zero E) unpredictable

What about this reactions suggests it is a "one-way" reaction It is happening all in the gas phase. It has a single, forward arrow. It is a synthesis reaction. It is balanced