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Chem I Lab > Exam 2 > Flashcards

Exam 2 Flashcards

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1
Q

What is an ionic equation?

A

A chemical equation that presents ionic compounds in the form in which they exist in aqueous solution
[ex: CaCl2 (s) –> Ca2⁺ + Cl⁻+ Cl⁻ ]

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2
Q

What are spectator ions?

A

Cations/Anions that don’t participate in any observable or detectable chemical reaction

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3
Q

What is a net ionic equation?

A

An equation that includes only those ions that participate in the observed chemical reaction

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4
Q

At which temperatures does Calcium Oxalate start to become two different compounds (CaC₂O₄·H₂O & CaC₂O₄)

A

CaC₂O₄ forms at temperatures above 110℃, while CaC₂O₄·H₂O is stable below ~90℃

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5
Q

Which filtration was used for the “Limiting Reactant” Lab

A

Gravity filtration

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6
Q

What were the two reactants for the “Limiting Reactant” Lab

A

Potassium Oxalate (K₂C₂O₄) & CaCl₂ (Calcium Chloride)

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7
Q

What were the products of the “Limiting Reactant” Lab

A

Calcium Oxalate (CaC₂O₄)

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8
Q

How do you find the precipitate in the “Limiting Reactant” Lab

A

You added the two reactants to two different tubes of your supernatant from the original salt

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9
Q

Define Supernatant

A

Clear solution that exists after the precipitate has settled

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10
Q

In the “Limiting Reactant” lab, how does the waste get disposed?

A) All aqueous waste can go down the sink with water (except any concentrated acids or bases) and all solid waste can go in regular trash
B) All aqueous waste should go in the aqueous waste barrel and all solid waste can go in regular trash
C) All aqueous waste should go in the aqueous waste barrel and all solid waste should go in the solid waste bin
D) All aqueous waste can go down the sink with water (except any concentrated acids or bases) and all solid waste can go in the solid waste bin

A

C

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11
Q

In the “Limiting Reactant” lab, how will failing to flute your filter paper affect your final yield….

A) Increase amount of product
B) Decrease amount of product
C) Not affect amount of product

A

C

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12
Q

Define a Calorimeter

A

Something that is used to measure the quantity and direction of heat flow accompanying a chemical or physical change

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13
Q

Heat change is quantitatively expressed as….

A

Enthalpy (Heat) of a reaction ΔH

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14
Q

If ΔH is postive, your reaction is…

A) Exothermic
B) Endothermic

A

B

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15
Q

If your ΔH is negative, your reaction is…

A) Exothermic
B) Endothermic

A

A

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16
Q

What is the specific heat of water

A

4.18 J℃

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17
Q

What is the formula for energy/heat

A

q = mcΔT

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18
Q

Is specific heat an extensive or intensive property…

A) Intensive
B) Extensive

A

A; meaning it is independent of sample size

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19
Q

How do you measure the heat of a metal that doesn’t react with water?

A

1) Get the mass of the metal
2) Heat the metal to a known (higher) temp.
3) Place it into a measured amount of water at a known (lower) temp.
4) Measure the final equilibrium temp of the system after the two are combined

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20
Q

What is the formula for determining the energy/heat lost by the metal?

A

-q (metal) = q (water)
or
-(q = mcΔT) = (q = mcΔT)

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21
Q

How do you calculate ΔT?

A

T (final) - T (initial)

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22
Q

What is ΔHₙ?

A

Enthalpy (Heat) of Neutralization of an Acid-Base Reaction

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23
Q

What are the products of a strong acid and strong base reaction

A

Water (H₂O) & Heat

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24
Q

What is the formula for ΔHₙ

A

ΔHₙ = -(specific heat of water)(combined mass of acid and bases)(ΔT)

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25
Is ΔHₙ expressed as... A) kJ/mol B) J/mol
A
26
Define Lattice Energy
Energy required to vaporize one mole of salt into its gaseous ions – an endothermic quantity
27
What does ΔH(LE) represent
Lattice Energy (endothermic); only deals with salts
28
Define Hydration Energy
Energy released when one mole of a gaseous ion is attracted to and surrounded by water molecules forming one mole of hydrated ion in aqueous solution – exothermic quantity
29
What does ΔH (hyd) represent
Hydration energy (exothermic); only deals with salts
30
What does ΔHₛ mean
Enthalpy (Heat) of solution
31
What is the formula for ΔHₛ *Hint* only deals with salts
= ΔH(hyd) + ΔH(LE)
32
How can you measure for ΔHₛ in the lab since ΔH(LE) and ΔH(hyd) are hard to measure?
Since we know that ΔH(LE) is endothermic, if the temperature decreased, we know that the ΔH(LE) > ΔH(hyd) for the salt If the temperature increases, we know that an exothermic reaction is taking place, therefore the ΔH(hyd) > ΔH(LE)
33
What is the formula for enthalpy of solution (ΔHₛ) experimentally?
ΔHₛ = (-energy change of water)(-energy change salt) ---------------------------------------------------------------------- mole of the salt
34
What is a good constant pressure calorimeter?
A set of nested coffee cups
35
Where do neutralized solutions contained in the calorimeter go?
They can go down the sink; since it's mostly water that's left as the two have been neutralized
36
A substance with small specific heat will up.... A) Quickly B) Slower
A
37
Heat is invariably lost to the calorimeter when you add the hot metal to the water at a lower temperature. Will this unmeasured heat loss increase or decrease the calculated value of the specific heat of the metal? A) Decrease B) Increase C) No effect
A
38
What is the strong acid that is used in Part B of the "Calorimetry" experiment to determine the enthalpy of neutralization A) Sulfuric B) Hydrochloric C) Perchloric D) Acetic
B or HCl
39
When plotting a standard curve using Beer's Law, you should plot... A) Absorbance on x-axis, molar concentration on y-axis B) Molar concentration on x-axis, transmittance on y-axis C) Transmittance on the x-axis, absorbance on y-axis D) Molar concentration on x-axis, absorbance on y-axis E) Absorbance on x-axis, transmittance on y-axis
D
40
In "Beer's Law" experiment, what was the total volume of the solution in the test tube A) 6 mL B) 3 mL C) 10mL
A
41
The Beer's Law is a mathematical expression that relates to... A) Amount of light absorbed by a substance to the concentration of the substance B) The amount of light transmission that a sample can emit C) The percent of light absorbed by a substance
A
42
In the "Beer's Law" experiment, what wavelength is being used to measure the sample.... A) 6.8 nm B) 510 nm C) Needs to be determined from a graph
B
43
If you fail to clean the cuvette prior to determining the concentration of your unknown in the "Beer's Law" experiment, your concentration will not be accurate A) True B) False
A
44
What is the purpose of a salt bridge A) To capture the chemical energy derived in the experiment B) To balance the charges from the half reactions C) To protect the electrodes from errosion
B
45
All solution in the "Galvanic Cells" lab will be disposed in the following manner... A) Pour down the drain B) Pour into the waste barrel
B
46
What salt was used in the "Galvanic Cells" lab A) Sodium Chloride B) Magnesium Chloride C) Potassium Nitrate D) Zinc Nitrate E) Sodium Sulfide F) Ammonium Sulfide
C
47
Which Galvanic cell was not measured in the "Galvanic Cell" lab A) Cu - Zn B) Zn - Mg C) Cu - Fe D) Zn - Fe
B
48
What is the formula for Beer's Law
A = ɛcl A = Absorbance (measurable w/ no units) ɛ = Extinction Coefficient (units M^-1cm^-1) c = concentration of the absorbing substance (regular concentration measurements) l = path length of the substance that the light passes through (units of cm)
49
Is Beer's Law a..... A) Linear relationship B) Exponential relationship
A; meaning that there is a direct link between concentration of a solution and how much light it will absorb
50
What is the only way that Beer's Law can be used by chemists?
It can only be used on sample with high purity and samples with the Extinction Coefficient being known
51
How do you determine the concentration of an unknown sample
Make a standard curve (excel graph), plot your absorbance, and find the concentration that goes with in (on x-axis)
52
What is the formula for calculating E° using cathodes and anodes numbers
E° (cell) = E° (cathode) - E° (anode)
53
What are electrodes
Usually metal strips/wires connected by an electrically conducting wire
54
How do you express Galvanic Cells in regard to cathodes and anodes
Anodes || Cathodes; this is because electrons flow from the anodes to the cathodes
55
What is the role of catalysts?
Lower the activation energy and affect the rate of the reaction
56
Do reactions get faster or slower as it proceeds A) Faster B) Slower
B; reactants are getting used up, so its getting slower to make those products
57
Which reagent binds with the triiodide ion to the deep-blue complex that signifies the end point of the rate reaction in part F? a. sulfurous acid b. iodic acid c. sulfuric acid d. water e. starch
E; Starch
58
Which factor will increase the reaction rate? a. decrease in pressure b. decrease in surface area c. increase in volume d. increase in concentration
D
59
A catalyst functions by ____. a. decreasing the overall energy required for a reaction b. increasing the overall energy given off from a reaction c. decreasing the energy required for the activation of a reaction d. increasing the energy required for the activation of a reaction
C
60
What is the visual signal to stop the experiment in Part A of the "Factors Affecting Reaction Rate"? a. absence of metal b. color change of metal c. change in pH d. change in temperature
A
61
In "Factors Affecting Reaction Rate", what is the independent variable of the experiment? (Part A) a. the concentration of the acid b. the composition of the acid c. the amount of metal d. the composition of the metal e. the presence of the catalyst
D
62
The ______ of a solution is the substance present in _______ amount(s) in the solution A) Solvent, smallest B) Solute, largest C) Solvent, Largest D) Solute Equal
C;

Chem I Lab (2 decks)

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