Chemistry

What is the deltaGrxn of this reaction, and would it be spontaneous or nonspontaneous at 300.0 K?

-100 kJ/mol, spontaneous

What is the enthalpy of combustion (per mole) of C3 H8 (g)?

-2,044.0 kJ/mol

How does the potential-energy diagram for a reaction indicate whether the reaction is endothermic or exothermic?

An endothermic reaction has reactants that are lower in energy than products because energy is absorbed to form the products.

Which reaction is exothermic?

CH4 + 2O2 -> CO2 + 2H2O + 891 kJ

Which statement describes a catalyst?

Catalysts provide a lower energy pathway for the reaction.

A welding torch produces a flame by burning acetylene fuel in the presence of oxygen. The energy released from the acetylene fuel is then used to melt a metal. Which energy transformation happens during this process?

Chemical energy turns into thermal energy.

A two-step reaction mechanism that has an overall reaction of 2H2O2(aq) mc012-1.jpg 2H2O(l) + O2(g) has the following fast step and rate law. Step 2: H2O2 + OI- mc012-2.jpg H2O + O2 + I- (fast) Rate = k[H2O2][I-] Which is the correct rate-determining step given the information in the reaction above?

D. step 1: H2O2 + I- mc012-6.jpg H2O + OI-

Which statement describes the law of conservation of energy?

Energy cannot be created nor destroyed, but it changes from one form to another.

Which energy changes are associated with a liquid freezing?

Energy is released as potential energy decreases.

Which reaction is an example of heterogeneous catalysis?

Ethene gas reacts with hydrogen gas by using a nickel catalyst.

The specific heat of water is 4.18 J/(gi°C) and that of wood is 1.97 J/(gi°C). Which statement is correct?

Given equal masses, water will heat up less than wood if the same heat is added.

An ice cube is placed on a kitchen counter. Which best describes heat flow in this situation?

Heat flows from the counter to the ice, causing the molecules in the counter to move more slowly.

Why does platinum metal make a good catalytic surface for reactant molecules?

It holds reactant molecules in a good position for them to react.

Chemical energy in burning wood is changed into thermal energy. The thermal energy is absorbed by water, which boils to produce steam. The thermal energy is changed into kinetic energy in the moving steam. The kinetic energy is used to turn a turbine, which converts the kinetic energy into electricity. Which sentence best describes this system?

It involves both energy transformation and energy transfer.

What overall effect does adding a catalyst have on a chemical reaction?

It lowers the activation energy that is needed.

Which statement describes how a basic coffee cup calorimeter works?

It uses the mass and specific heat of water along with a thermometer to measure the gain or loss of energy when a substance is added.

A student touches a freshly baked cake that was taken out of the oven. Which best explains why the cake feels hot?

Molecules in the cake are moving faster than molecules in the skin.

Which substance has delta Hf defined as 0 kJ/mol?

O2 (g)

Which catalyzed reaction breaks up ozone? 2H2O2(l) mc005-1.jpg 2H2O(l) + O2 O3 + O mc005-2.jpg 2O2 2H2O2 (aq) mc005-3.jpg 2H2O(l) + O2 O2 + 2SO2mc005-4.jpg 2SO3

O3 + O --> 2O2

Consider the two-step reaction mechanism that has an overall reaction of H2O2(aq) + 2I-(aq) mc033-1.jpg I2(aq) + 2OH-(aq). Step 1: H2O2(aq) + I-(aq) mc033-2.jpg HOI(aq) + OH-(aq) (slow) Step 2: HOI(aq) + I-(aq) mc033-3.jpg I2(aq) + OH-(aq) (fast) Which is the correct rate law for the overall reaction?

Rate = k[H2O2][I-]

Why are enzymes required for living things to function?

Reactions take place too slowly at body temperature and must be speeded up.

The temperature of a sample of liquid water changes from 50°C to 30°C. Which statement best explains the change that must happen at the molecular level?

The molecules move more slowly and their average kinetic energy decreases.

Which statement defines calorimeter?

a device that measures the heat that is gained or lost in a chemical change

What would be the greatest difference in using an open ceramic coffee mug rather than an insulated mug with a lid as a calorimeter?

exchange of energy with the surroundings

Which is the best example of potential energy?

holding a basketball in the air

Which characteristic of enzymes allows it to be highly specific in the reactions they catalyze?

its structure

Which is the best term to use when describing the energy of motion?

kinetic

Which is the best term to use when describing the energy of position?

potential

Which energy change best relates to a boulder that is rolling down the side of a hill?

potential energy transforming into kinetic energy

Which arrangement correctly categorizes the above processes into either spontaneous or nonspontaneous processes? spontaneous: i nonspontaneous: ii, iii, iv, v, vi spontaneous: i, ii, v nonspontaneous: iii, iv, vi spontaneous: i, ii, iii, iv, vi nonspontaneous: v spontaneous: i, v nonspontaneous: ii, iii, iv, vi

spontaneous: i, ii, iii, iv, vi nonspontaneous: v

Which defines the average kinetic energy of a system's particles?

temperature

Which statement defines the enthalpy of hydration?

the change in enthalpy when 1 mol of a gaseous ion becomes fully hydrated

What is thermal energy?

the kinetic energy of particles in a system

Which statement describes mechanical energy?

the sum of the kinetic energy and the potential energy of an object

Which form of energy is directly related to the measure of the average kinetic energy of the particles in a substance?

thermal energy

Two different gases are stored in separate closed containers. If both gases have a temperature of 50°C, which statement is true?

The gas molecules in both containers have the same average kinetic energy.

Which statement defines activation energy?

It is the difference between reactant energy and maximum energy.

Which statement describes a heterogeneous catalyst?

It is in a different phase than the reactants.

GF,NH3 = -16.66 kJ/mol GF,NO = 86.71 kJ/mol -228.6 kJ/mol -206.4 kJ/mol 46.7 kJ/mol 90.7 kJ/mol

-228.6 kJ/mol

Hrxn = -56.13 kJ Srxn = 87.1 J/K T = 303 K -82.5 kJ -29.7 kJ 26,500 kJ 27,000 kJ

-82.5

A sample of an unknown substance has a mass of 0.465 kg. If 3,000.0 J of heat is required to heat the substance from 50.0°C to 100.0°C, what is the specific heat of the substance?

0.129 J/(gi°C)

A reaction is shown below. Reaction : mc023-1.jpg What can be concluded about this reaction? A homogeneous catalyst is being used in the reaction. A heterogeneous catalyst is being used in the reaction. A catalyst is not being used in this reaction. An enzyme is being used in this reaction.

A heterogeneous catalyst is being used in the reaction.

What is S for the reaction N2(g) +O2(g) --> 2NO? Use G = 173.3 kJ at 303.0 K and mc009-4.jpgH = 180.7 kJ. Use G = H - T delta S.

24.42 J/K

Complete combustion of a 0.600-g sample of a compound in a bomb calorimeter releases 24.0 kJ of heat. The bomb calorimeter has a mass of 1.30 kg and a specific heat of 3.41 J/(gi°C). If the initial temperature of the calorimeter is 25.5°C, what is its final temperature?

30.9°C

Reactant X contains 199.3 J of chemical energy. Reactant Y contains 272.3 J of chemical energy. Product W contains 41.9 J of chemical energy. If the reaction loses 111.6 J of chemical energy as it proceeds, how much chemical energy must product Z contain?

318.1 J

When 40.0 mL of 1.00 M H2SO4 is added to 80.0 mL of 1.00 M NaOH at 20.00°C in a coffee cup calorimeter, the temperature of the aqueous solution increases to 29.20°C. If the mass of the solution is 120.0 g and the specific heat of the calorimeter and solution is 4.184 J/g • °C, how much heat is given off in the reaction? (Ignore the mass of the calorimeter in the calculation.)

4.62 kJ

The initial temperature of a bomb calorimeter is 28.50°C. When a chemist carries out a reaction in this calorimeter, its temperature decreases to 27.45°C. If the calorimeter has a mass of 1.400 kg and a specific heat of 3.52 J/(gi°C), how much heat is absorbed by the reaction?

5,170 J

This is the equation for the dissociation of ammonia gas at 293 K. deltaH = 145 kJ and deltaS = 195 J/k.

87.9 kJ, nonspontaneous

Marcela dissolves 80.0 g of ammonium nitrate in 50.0 mL of water at room temperature and notes that the temperature of the solution decreases by 5.0°C. Which correctly designates the signs of mc015-1.jpgH, mc015-2.jpgS, and mc015-3.jpgG for this reaction?

A .mc015-4.jpgH > 0, mc015-5.jpgS > 0, and mc015-6.jpgG < 0

Which units express specific heat capacity?

J/(gi°C), J/(giK), cal/(gi°C), cal/(giK)

Which units express heat capacity?

J/°C, J/K, cal/°C, cal/K

What happens to energy when Sally kicks a soccer ball?

Kinetic energy is transferred from the leg to the soccer ball.

What must occur for the enthalpy of solution to be negative?

More energy is released as the solute and solvent mix than is absorbed when the solute particles and the solvent particles separate.

The second reaction in the formation of sulfuric acid occurs slowly. NO2 is added to the reaction to speed it up. In which form would this substance be a homogeneous catalyst for this reaction?

NO2(g)

Which answer defines exothermic reaction?

a process in which energy is released as heat

Iron reacts with oxygen in a chemical hand-warmer. How should this reaction be categorized?

as an exothermic process because it releases heat

Thermal energy is the energy associated with

Temperature