Unit 8 Chem

Energy from a reaction was determined to be 3870 J using a water calorimeter, when burning 9.00 grams of H2. What is the total enthalpy of the reaction?

-0.867 kj/mol

A calorimeter is used to measure the combustion of 14.0 grams of H2 gas under 150. grams of water. The energy measured using the water was 10,432 J. What is the heat lost or gained by the total reaction?

-1.49 kJ/mol

Energy from a reaction was determined to be 11563 J, when burning 15.0 grams of H2. What is the total enthalpy of the reaction?

-1.54 kJ/mole

A calorimeter is used to measure the combustion of 5.00 grams of H2 gas under 62.0 grams of water. The energy measured using the water was 4,432 J. What is the heat lost or gained by the total reaction?

-1.79 kj/mol

A 2.50 gram sample of CH4 is burned in a calorimeter. The calorimeter is filled with 100.0 grams of water. The temperature of a calorimeter increases from 20.0°C to 30.0 C. Calculate the energy lost or gained by the reaction in kJ per mole.

-26.8 kJ/mole

A 3.50 gram sample of CH4 is burned in a calorimeter. The calorimeter is filled with 35.0 grams of water with a specific heat of 4.184 j/gC' . The temperature of a calorimeter increases from 25.0°C to 30.0°C. Calculate the energy lost or gained by the reaction.

-3.36 kj/mol

A calorimeter is used to measure the combustion of 8.00 grams of H2 gas under 75.0 grams of water. The energy measured using the water was 15,400 J. What is the heat lost or gained by the total reaction?

-3.85 kJ/mol

Molecule ΔH (kJ/mol) C 0 O2 0 CO2 -393.52 C + O2 \longrightarrow ⟶ CO2 Calculate the enthalpy for the equation above.

-393.52 kJ/mole

The initial temperature of water is 30.0 °C, and the final temperature is 25.0 °C. What is the change in temperature of the water.

-5.0 °C

Convert 22.1 grams of CO2 into moles.

0.500 moles

Convert 28.1 grams of CO2 into moles.

0.639 moles

Convert 22.3 grams of CH4 into moles of CH4.

1.39 moles

A reaction heats up 50.0 grams of water from 22.0 °C, to 28.0 °C. Water has a specific heat of 4.184. How much energy was released?

1260 J

A reaction heats up 150.0 grams of water from 22.0 °C, to 29.0 °C. Water has a specific heat of 4.184. How much energy was released?

4390 j

Molecule ΔH (kJ/mol) H2O -285.82 H2 (g) 0 O2 (g) 0 2H2O --> 2H2 + O2 Calculate the enthalpy for the equation above.

571.64 kJ/mol

Convert 7593 J into kJ.

7.593

The initial temperature of water is 15.0 °C, and the final temperature is 23.0 °C. What is the change in temperature of the water?

8.0 °C

Which of the statements below are true regarding systems and surroundings?

A system is where the reaction occurs, while the surroundings are everything outside of that reaction

An unknown sample with a mass of 2.59 grams gains 28.0 J of energy, and has a temperature change of 12.0 °C. What is the identity of the unknown sample? Sample Specific heat values Aluminum 0.90 Lead 0.13 Iron 0.45 Water 4.184

Aluminum

What type of energy is the energy found in the bonds of molecules?

Chemical

A hand warmer consists of two layers. The inner layer contains two chemicals separated by a thin plastic coating. The outer layer is thicker, and protects users from exposure to chemicals. What two types of energy are seen if the inner plastic layer is broken, allowing the chemicals to mix and produce heat?

Chemical and Thermal

A hot pack gets hot after the molecules inside the container react. Based only on the information provided, what energy changes are occuring?

Chemical to Thermal

Which type of energy is correctly paired with its description?

Chemical: energy found in the bonds between atoms

A reaction's reactants possess 200.0 kJ of energy, and its products possess 250.0 kJ of energy. What type of reaction is this?

Endothermic

An ice cube melts on your hand. This is an example of an ______________ reaction.

Endothermic

Which of the following is true for the 1st law of thermodynamics;

Energy can be transferred

A campfire is an example of an _____________ reaction.

Exothermic

A reaction gives an enthalpy (ΔH) value of -1283.0 kJ/mol. This reaction is;

Exothermic

A reaction's reactants possess 400.0 kJ of energy, and its products possess 200.0 kJ of energy. What type of reaction is this?

Exothermic

Molecule ΔH (kJ/mol) H2O (l) -286.0 H2O (g) -242.0 H2O (l) \longrightarrow ⟶ H2O (g) Using the information available in the chart above, solve for the energy change in the equation provided. After solving for the energy value, label the equation as being exothermic or endothermic.

H2O (l) --> H2O (g) -286.6 --> -242.0 -242.0 -286.0 44.0 kJ/mole the reaction is Endothermic

Cooking pots are used to transfer heat to food and cook it and they can be made of many different materials. Using the following information about various pots, which material would you choose for a pot? Substance that the pot is made of Characteristics of that substance Iron Holds thermal energy, does not react when chemical changes occur inside of it Wood Does not hold thermal energy, does not react when chemical changes occur inside of it Aluminum Holds thermal energy, reacts when chemical changes occur inside of it Paper Does not hold thermal energy, reacts when chemical changes occur inside of it

Iron

What type of energy is associated with movement?

Kinetic

A rock is perched upon a cliff. It has __________ energy.

Potential

What type of energy is stored energy?

Potential

A pool player uses the cue stick to strike the cue ball sending it down the pool table. The cue ball gently hits the eight ball, sending it into a nearby pocket. Based only on the information provided, what two forms of energy are present in this example?

Potential and Kinetic

An Olympic high diver stands on the edge of a diving board before gracefully diving into the water. Based only on the information provided, what two forms of energy are present in this example?

Potential and Kinetic

Which part of a reaction has more energy for an endothermic reaction?

Products

A reaction heats up 100.0 grams of water from 22.0 °C, to 29.0 °C. Water has a specific heat of 4.184 LaTeX: \frac{J}{g\:^\circ C} J g ∘ C . How much energy was absorbed?

Q=2930J

Which part of a reaction has more energy for an exothermic reaction?

Reactants

A cold piece of iron is placed inside of an empty bowl. Boiling water is poured on top of the iron. Which of the following is true about this experiment:

The metal will get warmer because the water will add energy to it.

A piece of zinc is placed over a Bunsen burner until it starts to melt. While still mostly solid, the zinc is dropped into a beaker of cool water. Which of the following is true about this experiment:

The metal will transfer energy to the water, making the water get warmer.

Before a chemical reaction begins, reactants of a chemical equation have 200.0 kJ of energy. After the reaction has completed, the products now have 450.0 kJ of energy. Which of the following is true about this reaction?

The reaction is endothermic, 250.0 kJ of energy were absorbed, the enthalpy value for this reaction is positive.

Before a chemical reaction begins, reactants of a chemical equation have 300.0 kJ of energy. After the reaction has completed, the products now have 550.0 kJ of energy. Which of the following is true about this reaction?

The reaction is endothermic, 250.0 kJ of energy were absorbed, the enthalpy value for this reaction is positive.

Find the statement below that would be true about the following equation; 571.64 + 2H2O ⟶ 2H2 + O2

The reaction is endothermic, The reaction is gaining energy

Find the statement below that would be true about the following equation; CH4 + O2 ⟶ CO2 + H2O + 785 kJ/mol

The reaction is exothermic, The reaction is losing energy

What type of energy is heat energy?

Thermal

A cup of hot chocolate becomes cold when it loses its energy after sitting out too long. What type of energy is being described?

Thermal Energy

Which of the following is false regarding the process of determining ΔH using Calorimetry.

To convert J into kJ multiply by 1000

true or false Energy can be transferred from one substance to another?

True

Spatulas are a cooking utensil used for flipping food as it cooks and they can be made out of many different materials. Using the following information about various spatula materials, which material would you prefer to cook with? Substance that the spatula is made of Characteristics of that substance Iron Holds thermal energy, does not bend when exposed to kinetic energy Wood Does not hold thermal energy, does not bend when exposed to kinetic energy Aluminum Holds thermal energy, Bends when exposed to kinetic energy Paper Does not hold thermal energy, bends when exposed to kinetic energy

Wood

Calorimeter

a device used to measure the amount of heat involved in a reaction or process.

Calorimetry

a process used to determine the amount of heat involved in a reaction or process.

Temperature

average kinetic energy of a group of molecules.

Delta

commonly referred to as change. The way to find a delta is to take the final value, and subtract the initial value.

Thermal Energy

commonly referred to as heat energy.

According to the first law of thermodynamics, energy cannot be _______ or _______. But it can be ____________.

created, destroyed, transferred

Surroundings

everything outside of a system.

true or false Energy can be destroyed

false

true or false ΔH is measured in J/mole

false

true or false A thermometer works by directly measuring the amount of heat energy around it.

false (a thermometer measures the amount of kinetic energy from molecules.)

true or false Temperature measures heat

false (temperature measures the kinetic energy of molecules, heat measures energy)

An unknown mass of water is heated from 24.0 °C to 30.0 °C. Water has a specific heat capacity of 4.184. If 221 J are absorbed by the water during the heating, what is the mass of the water?

m= 8.80 g

A sample of salt is placed within a Styrofoam cup filled with water. The salt dissolves rapidly. The water inside the cup gets colder, while the cup stays the same temperature. The salt is the _______, while the water is the ___________.

system, surroundings

Enthalpy

the complete amount of heat inside of a system.

You light a campfire to cook s'mores. The system for this reaction is ___________, and the surroundings are ___________.

the logs burning on the fire; everything outside of the fire

true or false A rock rolling down a hill involves the transfer of potential energy into kinetic energy.

true

true or false ΔH is measured in kJ/mol

true

Liquid water is placed into a freezer. Heat transfers from the __________ to the ________, resulting in an ___________ process.

water, freezer, exothermic

Endothermic

when a reaction or process gains energy from the surroundings to the system.

Exothermic

when a reaction or process loses energy from the system to the surroundings.