Unit Six Thermochemistry and rate
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| A 20 gram piece of metal is added to a sample of 100 grams of water inside a calorimeter. If the metal is at a temperature of 125° Celsius and the water is at 20° Celsius, which of the following best describes what will occur inside the calorimeter? | the energy lost by the metal equals the energy gained by the water.
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| Which of the following is the best example of an open system? | a car engine.
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| Which of the following statements is true for an exothermic reaction? (2 points) | the products have lower potential energy then the reactants and the enthalpy change is negative.
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| If an endothermic reaction is conducted inside a calorimeter filled with water, which of the following statements is not correct regarding the reaction? | the total energy inside the calorimeter will increase.
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| If a reaction is not spontaneous at any temperature, what is true of the reaction? | it has a positive enthalpy and negative entropy change.
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| Alexis is observing a reaction that is taking place in an unsealed glass beaker. Is Alexis's experimental setup an example of a closed, open, or isolated system? Explain your answer in complete sentences. | the reaction she is viewing is an open system because the glass beaker is open, so energy, can escape and go into the glass.
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| Predict how the addition of a catalyst would affect the rate of the reaction below, and explain your prediction. H2 (g) + I2 (g) 2 HI (3 points) | the catalyst is supposed to increase the rate of reaction, so this would mean that the reaction between iodine and hydrogen would be much quicker.
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| Which reaction shows decrease in entropy? | Cao(s)+H2O(l)---> Ca(OH)2(s).
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| When aqueous solutions of HCl and NaOH are mixed together in a calorimeter, the temperature of the solution increases. The reaction is (2 points) | exothermic, causing an increase in the kinetic energy of the water molecules.
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| 4130 J of energy is added to a 52g sample of water that has and initial temperature of 10.0 C. I the specific heat of water is 4.18J/(gxC), what would the final temp of the water be? | 29 C.
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| According to collision theory, what happens in a reaction without sufficient energy or correct orientation? | no products will be formed.
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| An increase in the temperature of a liquid causes a(n) | increase in the kinetic energy of the particles.
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| a metal pot is filled with water and placed on top of a stove. As the stove top heats up, the water begins to boil and steam can be seen escaping from the pot. This is and example of a(n) | open system because heat and matter are both able to enter and the leave the system.
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| what statement best describes a closed system? | energy can be exchanged between system surroundings but matter cannot
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| What best describes the potential energy diagram of an endothermic process? | the potential energy value of the reactants is less than that of the products.
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| Which answer best describes the potential energy diagram for a reaction that takes place in water, if the temperature surrounding water is lowered? | the potential energy of the reactants is low; the potential energy increases gradually; it peaks, then decreases slightly.
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| describe how you would use the information depicted on the potential energy diagram below to determine the amount of required activation energy and the enthalpy change of the reaction. | delta H is the potential energy of the products subtracted by the potential energy of the reactants. This would be our C-A which would give us our delta H. Our activation energy would be B-A. This then gives us the energy we need to start our reaction.
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| an endothermic process is one in which heat is blank from its surroundings. | gained.
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| When a calorimeter is used, no heat is shared between the contents of the container and the outside air. If an endotherm. reaction is made inside a calorimeter filled with water, which of the following statements is not correct regarding the reaction? | the total energy inside the calorimeter will increase.
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| the specific heat of copper metal is 0.385 J/(g* C). How much energy must be added to a 35.0 gram sample of copper to change the temperature from 20.0 C to 65.0 C? | 606 J.
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| 31.5 grams of a new substance is heated to 102.4 deg. C and then placed into a calorimeter holding 103.5 grams of water at 24.5 degrees C. If the final temperature reached in the calometer is 32.5 degrees C, what is the specific heat of the new substance? | msDT = msDT
m = mass
s = specific heat
DT = change in temperature
(31.5)(102.4-32.5)
= (103.5)(4.18)(32.5-24.5)
2201.85x
= 3464.352
x = 1.57 J/(° C × g).
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| a sample of gas has increase In temperature from 20 C to 22 C. What happens as the temperature of the gas goes up? | the kinetic energy of the particles increases.
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| Which of the following changes would increase the rate of a reaction between vinegar and sodium hydroxide? | heating up the vinegar.
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| what is a good example of s closed system? | a greenhouse.
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| Which term below best matches a potential energy diagram in which the potential energy value of the reactants is less than that of the products? | endothermic process
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| What is an example of an endothermic process? | a chocolate bar melting in the car.
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| Which of the following statements is true for an exothermic reaction? | the products have lower potential energy than the reactants, and the enthalpy change is negative.
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| When a calometer is used, no heat is traded between the contents of the dish and the outside air. If an exothermic reaction is shown inside a calometer filled with water, which of the following statements best describes what occurs during the reaction? | the total energy inside the calorimeter is conserved.
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| A 20 gram piece of metal is added to a sample of 100 grams of water inside a calorimeter. If the metal is at a temperature of -5° Celsius and the water is at 20° Celsius, which of the following best describes what will occur inside the calorimeter? | the energy gained by the metal equals the energy lost by the water.
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| 35.5 grams of an unknown substance is heated to 103.0 degrees C and then placed into a calorimeter containing 100.0 g of water at 24.0 C. If the final temperature reached in the calorimeter is 29.5 C, what is the specific heat of the unknown substance? | (35.5)(103-29.5)(x)=(100)(29.5-24.0)(4.18)= .89J/g C.
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| what do chemists say has to happen for compounds, ions or atoms to react successfully? | that particles must collide together.
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| What is the collision theory based on? | the collision theory is based on the idea that the rate of a reaction is determined by the number of successful collisions that occur over a given amount of time
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| what happens in a successful collision? | it results in the making of a product.
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| what two factors must be true for a collision to be correct. | sufficient energy and correct orientation.
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| what is an example of a isolated system? | our universe.
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| what is an example of a closed system? | earth.
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| what is an example of an open system? | our bodies.
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| what is an isolated system? | no matter or energy is allowed to be exchanged w/ the surroundings. the total amount of energy is constant because it cannot leave or enter
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| what is an open system? | matter and energy can be exchanged freely between systems and surroundings.
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| what is a closed system? | energy can leave and enter as it chooses but matter cannot.
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| what is entropy? | the property that describes the disorder of a system.
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| is freezing water into ice an increase or decrease in entropy? | decrease.
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| is dissolving salt in H2O an increase or decrease in entropy? | increase.
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| is evaporatingg rubbing alcohol in increase or decrease in entropy? | increase.
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| is Co2+CaO----> CaCo3 in increase or decrease in entropy? | decrease.
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| is 2KClO3---->2KCl+3O2 an increase or decrease in entropy? | increase.
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| what is activation energy? | the minimum amount of energy required to initiate a chemical reaction.
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| what is thermochemistry? | the study of the changes in the energy that accompany chemical reactions and physical changes.
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| What can we not assume when doubling the concentration of one of the reactants? | We cannot assume that by doubling the concentration of one of the reactants you will double the rate of the reaction. The amount by which an increase in concentration increases the rate of a reaction depends on many different properties of the reaction.
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| What does increasing the temperature of a system increase? | it increases the rate of a reaction.
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| The direct relationship between temperature and rate is due to two reasons, both related to the collision theory, what are they? | Increasing the temperature of a system increases the average kinetic energy of the particles. This means more collisions between the reactants will have enough energy to react successfully.
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| The direct relationship between temperature and rate is due to two reasons, both related to the collision theory, what are they? | ke of the particles, meaning that the particles are going fasterThis means that there are more coll/min at a high temp than in the same sys at a low tempHaving more coll in a given time means there are more opp for coll to meet both req for suc.
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| What is a catalyst? | is a substance that speeds up a reaction without being consumed by the reaction.
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| what if the temp cant be increased? | If temp can't be raised to meet the ae req of a reaction, another way to speed up the reaction is to provide an alter reaction pthw with a low ae req. in the PED below, a cat provides a diff pthw btw reactants&prod that req a low amnt of ae.
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| For an exothermic reaction, what would the potential energy diagram most likely look like? | a curve indicating that the potential energy of the reactants is higher than the products.
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| When a given reaction is conducted in a calorimeter, energy is absorbed from the surrounding water and results in a decrease in the water's temp. Which of the following best describes the difference in the pe of the reactants and prod in this reaction? | The potential energy (pe)of the reactants is much lower than that of the products
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| Which of the following statements correctly describes the melting process? | It is endothermic because heat is gained from the surroundings.
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| 31.5 g of an unknown substance is heated to 102.4 C and then placed into a calorimeter containing 103.5 g of water at 24.5 C. If the final temperature reached in the calorimeter is 32.5 C, what is the specific heat of the unknown substance? | For the water, 103.5 x 4.18 x 8 (32.5-24.5=8) = 3461.04
For the metal, 31.5 x ? x 69.9 = 3461.04
I kept substituting numbers in for the ? until I found the answer, the specific heat (heat capacity) is 1.572 J
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| Inside a calorimeter, two solutions are mixed and result in an exothermic reaction. Which of the following best illustrates how this reaction affects the water in the calorimeter? | The reaction causes the temperature of the water to increase. The kinetic energy of the water molecules increases.
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| Mike is conducting an experiment inside an Erlenmeyer flask, and he has the top of the flask sealed with a balloon to capture any gaseous products that may be produced. What is Mike's experimental setup an example of? | closed because the energy can come and go but the matter cannot.
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| Predict whether the changes in enthalpy, entropy, and free energy will be positive or negative for the boiling of water, and explain your predictions. How does temperature affect the spontaneity of this process? | There will be a higher entropy, as the (l) is becoming a gas. enthalpy goes up cuz this is an endo reaction. there will be more free energy as this will be a gas. As this is an endo reaction, it will likely not be spon., as a higher temp is less spon.
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| According to collision theory, for a reaction to be successful, it must have correct orientation of the atoms of the reactants. Which of the following must also be present for a successful reaction to occur? | sufficient energy
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| What would diluting the vinegar do to the rate of a reaction between vinegar and sodium hydroxide? | decrease the rate of the reaction
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| Which statement below best describes how the catalyst affected the reaction rate shown in this diagram?(endo) | The addition of the catalyst decreased the activation energy of the reactants and sped up the reaction.
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| Use the collision theory to explain how increasing the temperature of a reaction will affect the rate of the reaction. | An inc in temp would make the rr much higher, b/c of the amount of collisions that would be taking place. When you have two items collided and the temp has inc the reaction will occur a lot quicker. If the temp dec the reaction will occur slowly.
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