FiltersDone

Question type

Essay

Multiple Choice

Short Answer

True False

Matching

Exam 6: Thermochemistry

Show Answer

Share

---

All types

Filters

Study FlashcardsPractice ExamLearn

Question 21

Multiple Choice

Review LaterAdd Note

Review Later

The enthalpy of fusion of ice is 6.020 kJ/mol.The heat capacity of liquid water is 75.4 J/mol·°C.What is the smallest number of ice cubes at 0°C,each containing one mole of water,necessary to cool 500 g of liquid water initially at 20°C to 0°C?

A) 1
B) 7
C) 14
D) 15
E) 126

Correct Answer

verified

Show Answer

Question 22

Multiple Choice

Review LaterAdd Note

Review Later

If a student performs an endothermic reaction in a calorimeter,how does the calculated value of $\Delta$ H differ from the actual value if the heat exchanged with the calorimeter is not taken into account?

A) " $\Delta$ H_calc" would be more negative because the calorimeter always absorbs heat from the reaction.
B) " $\Delta$ H_calc" would be less negative because the calorimeter would absorb heat from the reaction.
C) " $\Delta$ H_calc' would be more positive because the reaction absorbs heat from the calorimeter.
D) " $\Delta$ H_calc" would be less positive because the reaction absorbs heat from the calorimeter.
E) " $\Delta$ H_calc" would equal the actual value because the calorimeter does not absorb heat.

Correct Answer

verified

Show Answer

Question 23

Multiple Choice

Review LaterAdd Note

Two metals of equal mass with different heat capacities are subjected to the same amount of heat.Which undergoes the smallest change in temperature?

Which of the following statements is/are true? I.q (heat) is a state function because $\Delta$ H is a state function and q = $\Delta$ H. II.When 50.0 g of aluminum at 20.0°C is placed in 50.0 mL of water at 30.0°C,the H₂O will undergo a smaller temperature change than the aluminum.(The density of H₂O = 1.0 g/mL,specific heat capacity of H₂O = 4.18 J/g°C,specific heat capacity of aluminum = 0.89 J/g°C) III.When a gas is compressed,the work is negative since the surroundings are doing work on the system and energy flows out of the system. IV.For the reaction (at constant pressure) 2N₂(g) + 5O₂(g) $\to$ 2N₂O₅(g) ,the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps.

CH₄(g) + 4Cl₂(g) $\to$ CCl₄(g) + 4HCl(g) , $\Delta$ H = -434 kJ Based on the above reaction,what energy change occurs when 1.2 moles of methane (CH₄) reacts?

The following statements concerning petroleum are all true except:

In the lab,you mix two solutions (each originally at the same temperature) and the temperature of the resulting solution decreases.Which of the following is true?

The $\Delta$ H value for the reaction is -90.8 kJ.How much heat is released when 66.9 g Hg is reacted with oxygen?

Which of the following statements correctly describes the signs of q and w for the following exothermic process at P = 1 atm and T = 370 K? H₂O(g) $\to$ H₂O(l)

You take 295.5 g of a solid at 30.0°C and let it melt in 425 g of water.The water temperature decreases from 85.1°C to 30.0°C.Calculate the heat of fusion of this solid.

Given the equation S(s) + O₂(g) $\to$ SO₂(g) , $\Delta$ H = -296 kJ,which of the following statement(s) is (are) true? I.The reaction is exothermic. II.When 0.500 mole sulfur is reacted,148 kJ of energy is released. III.When 32.0 g of sulfur are burned,2.96 $\times$ 10⁵ J of energy is released.

__________ involves the transfer of energy between two objects due to a temperature difference.

If 5.0 kJ of energy is added to a 15.5-g sample of water at 10.°C,the water is

The heat combustion of acetylene,C₂H₂(g) ,at 25°C is -1299 kJ/mol.At this temperature, $\Delta$ H_f° values for CO₂(g) and H₂O(l) are -393 and -286 kJ/mol,respectively.Calculate $\Delta$ H_f° for acetylene.

For the reaction H₂O(l) $\to$ H₂O(g) at 298 K and 1.0 atm, $\Delta$ H is more positive than $\Delta$ E by 2.5 kJ/mol.This quantity of energy can be considered to be

A 45.9 g sample of a metal is heated to 95.2°C and then placed in a calorimeter containing 120.0 g of water (c = 4.18 J/g°C) at 21.6°C.The final temperature of the water is 24.5°C.Which metal was used?

When a system performs work on the surroundings,the work is reported with a negative sign.

On a cold winter day,a steel metal fence post feels colder than a wooden fence post of identical size because:

A fuel-air mixture is placed in a cylinder fitted with a piston.The original volume is 0.310-L.When the mixture is ignited,gases are produced and 935 J of energy is released.To what volume will the gases expand against a constant pressure of 635 mmHg,if all the energy released is converted to work to push the piston?

The heat of formation of Fe₂O₃(s) is -826.0 kJ/mol.Calculate the heat of the reaction when a 53.99-g sample of iron is reacted.