Chem 102 Pre-Lab Quiz (Thermochemistry, Colligative Properties, Chemical Kinetics: Beer's Law and Integrated Rate Laws, Chemical Kinetics: Initial Rates Method)

Learning objectives of the Thermochemistry experiment include:

Select one or more:

Demonstrating Newton's Law of Heating and Cooling.

Observing the reaction of NaOH solid with a 1.25 M solution of citric acid.

Using calorimetry to relate measured temperature changes in chemical reactions to the reactions' thermochemical properties.

Demonstrating concepts, terms, and calculations of thermochemistry.

Illustrating the concept of a state function for heats of reaction.

Using calorimetry to relate measured temperature changes in chemical reactions to the reactions' thermochemical properties.

Demonstrating concepts, terms, and calculations of thermochemistry.

Illustrating the concept of a state function for heats of reaction.

In an exothermic reaction, will the enthalpy change be positive or negative? Why?

Select one:

Enthalpy change will be negative; the energy of the starting material is higher than the energy of the products.

Enthalpy change will be positive; the energy of the starting material is higher than the energy of the products.

Enthalpy change will be negative; the energy of the starting materials is lower than the energy of the products.

Enthalpy change will be positive; the energy of the starting materials is lower than the energy of the products.

Enthalpy change will be negative; the energy of the starting material is higher than the energy of the products.

Hess's Law states that if a reaction can be written as the sum of two or more other reactions, the enthalpy change (ΔH) for the overall process must be the sum values of the constituent reactions.

Select one:

True

False

True

Enthalpy change ( ΔH ) is referred to as a "path function" because it is dependent on the specific mechanism of reaction, or pathway.

Select one:

True

False

False

According to the Safety Data Sheet (SDS) for hydrochloric acid (HCl) the following statements are listed as hazard statements?

Select one:

May be corrosive to metals.

May cause respiratory irritation.

Causes severe skin burns and eye damage.

All of the above.

All of the above.

Why do you weigh the solid NaOH by difference instead of directly weighing it on a weigh boat?

Select one:

The mass of the weigh boat would lead to a less precise measurement.

Sodium hydroxide is hygroscopic and will absorb water from the air, making it difficult to get an accurate mass.

Sodium hydroxide absorbs CO2 from the air and will cause the mass to be inaccurate

Sodium hydroxide is hygroscopic and will absorb water from the air, making it difficult to get an accurate mass.

What is the balanced chemical reaction and the net ionic reaction for reaction 3, NaOH solid in HCl?

Select one:

Balanced: NaOH(s) + HCl (aq) ---> NaCl(aq) + H2O(l)

Net ionic: NaOH(s) + H^+(aq) ---> Na+(aq) + H2O(l)

Balanced: NaOH(s) + HCl (l) ---> NaCl(aq) + H2O(l)

Net ionic: OH^-(aq) + H^+(l) ---> H2O(l)

Balanced: NaOH(s) + HCl (l) ---> NaCl(aq) + H2O(l)

Net ionic: NaOH(s) + H^+(l) ---> Na+(aq) + H2O(l)

Balanced: NaOH(s) + HCl (aq) ---> NaCl(aq) + H2O(l)

Net ionic: OH^-(aq) + H^+(aq) ---> H2O(l)

Balanced: NaOH(s) + HCl (aq) ---> NaCl(aq) + H2O(l)

Net ionic: NaOH(s) + H^+(aq) ---> Na+(aq) + H2O(l)

Calculate ΔH°rxn for the following reaction using the appropriate ΔH°f values, which can be found in the lab manual.

NaOH(s) + H^+(aq) + Cl^-(aq) ---> Na+(aq) + Cl^-(aq)+ H2O(l)

If needed, refer to the lab manual for an example calculation of the ΔH°rxn for the decomposition of water.

Select one:

-100.33 kJ/mol

44.5 kJ/mol

-44.5 kJ/mol

-58.8 kJ/mol

-100.33 kJ/mol

Important PPE for this lab includes:

Select one or more:

Lab coat

Fully enclosed shoes, clothes covering entire torso/midriff/shoulders and entire lower body

Goggles (to be worn at all times in the lab space)

Gloves (to be worn at all times manipulating the experimental set-up)

Gloves (to be worn at all times, even on a computer)

Lab coat

Fully enclosed shoes, clothes covering entire torso/midriff/shoulders and entire lower body

Goggles (to be worn at all times in the lab space)

Gloves (to be worn at all times manipulating the experimental set-up)

The main purpose for the Colligative Properties experiment is to:

Select one:

define what a colligative property is.

to identify an unknown acid dissolved in stearic acid through the colligative property of freezing point depression.

experimentally determine what the definition of molality is.

navigate through the procedure and collect data.

to identify an unknown acid dissolved in stearic acid through the colligative property of freezing point depression.

A colligative property depends upon the number of solute particles present and is not dependent upon the specific chemical identity of the solute.

Select one:

True

False

True

The following freezing temperatures will be recorded in this lab. (Select all that apply)

Select one or more:

The solution of stearic acid with water

The solution of stearic acid with an unknown fatty acid

The solution of unknown fatty acid with water

The pure solvent, unknown acid

The pure solvent, stearic acid

The pure solvent, water

The solution of stearic acid with an unknown fatty acid

The pure solvent, stearic acid

Describe the expected experimental apparatus you will use to determine the freezing point of the fatty acid samples.

Select one:

The smaller test tube must be wrapped in a paper towel and fitted into the larger test tube. The large test tube is secured on the ring stand using a clamp and positioned over the beaker of water on the hot plate. A Vernier temperature probe is placed in the water to record the water temperature.

The smaller test tube must be wrapped in a paper towel and fitted into the larger test tube. The large test tube is secured on the ring stand using a clamp and positioned over the hot plate. A Vernier temperature probe is placed inside the smaller test tube to record the fatty acid temperature.

A large test tube and a small test tube are clamped over a beaker of boiling water. The alcohol thermometer is placed in the water to monitor the water temperature.

The smaller test tube must be wrapped

The smaller test tube must be wrapped in a paper towel and fitted into the larger test tube. The large test tube is secured on the ring stand using a clamp, higher up than the beaker of water on the hot plate and away from any rising steam. An alcohol thermometer is placed in the small test tube to monitor the fatty acid temperature.

In part D of the COL procedure, the unknown fatty acid will be added to the same stearic acid sample which was used in part C to measure the freezing point of pure solvent.

Select one:

True

False

True

At different altitudes, the predicted van't Hoff factor of a chemical compound dissolved in an ideal solution will change.

Select one:

Yes! The lower the boiling point, the more likely it is that the dissolved solute will dissociate into discrete particles.

No, the predicted van't Hoff factor depends on the identity of the solute compound.

Yes! Atmospheric pressure affects the ability of a dissolved compound to dissociate into discrete solute particles.

No, the van't hoff factor is only dependent on the concentration of total solute particles dissolved in any given solution.

No, the predicted van't Hoff factor depends on the identity of the solute compound.

Rank the following solutes from smallest to largest observed freezing point depression in water (Kf = 1.86 °C/m, with m = molal)

0.8 m LiCl

0.5 m MgCl2

0.2 m CuCl2

1.2 m acetone

Select one:

A

C

A solution containing 20.0 g of an unknown non-electrolyte liquid and 110.0 g water has a freezing point of -1.32 °C. Given Kf = 1.86°C/m for water, the molar mass of the unknown liquid is:

Select one:

28 g/mol

71 g/mol

128 g/mol

256 g/mol

256 g/mol

Important PPE/attire for this lab includes: (Select all that apply)

Select one or more:

Goggles (worn over eyes at all times in the lab space)

Lab coat (worn buttoned at all times in the lab space)

Gloves (worn at all times when manipulating the experimental set-up)

Shoes that fully enclose feet; pants/skirt and socks that overlap to fully cover legs and ankles

Gloves (worn at all times even on a computer)

Goggles (worn over eyes at all times in the lab space)

Lab coat (worn buttoned at all times in the lab space)

Gloves (worn at all times when manipulating the experimental set-up)

Shoes that fully enclose feet; pants/skirt and socks that overlap to fully cover legs and ankles

The rate of the chemical reaction can be monitored via Beer's law and spectrophotometer absorbance reading; as the reaction moves in a forward direction, the concentration of crystal violet analyte in solution will Choose...increase/decrease and the absorbance reading will Choose...increase/decrease

Decrease/Decrease

Using the method of integrated rate laws, I am trying to determine the reaction order with respect to A in the following reaction: 2A + B ---> A2B

I made three plots: concentration of A (units of molarity, M) vs time (s); the natural logarithm of the concentration of A vs time (s); and the inverse concentration of A (M-1) vs time (s).

The following graph yielded a straight line:

Based on your pre-lab reading, what is the order of the reaction with respect to and what are the units of the slope ?

Select one:

This is a second order reaction with respect to A. The units on the slope are M-1s-1.

This is a second order reaction with respect to A. The units on the slope are M/s.

This is a first order reaction with respect to A. The units on the slope are M/s.

This is a first order reaction with respect to A. The units on the slope are M-1s-1.

This is a second order reaction with respect to A. The units on the slope are M-1s-1.

When using a micropipette, it is important to maintain a vertical orientation of the device with the tip pointing towards the floor. This will prevent any corrosive liquids from entering the pipette.

True

False

True

The Beer's Law relationship is how we will solve for the molar absorptivity coefficient. What is the equation that translates to the linear regression format?

Select one:

C = A m

C = A e

A = m[analyte] + b

A = I/Io

A = m[analyte] + b

Molar absorptivity coefficients are dependent upon both the specific analyte and the wavelength of light.

Select one:

True

False

True

The spectrophotometer requires what apparatus to collect data?

Select one or more:

Vernier Graphical Analysis software

Optical fiber cable

Plastic transfer pipette

Syringes

Vernier Spectral Analysis software

Cuvettes

Vernier Spectral Analysis software

Cuvettes

True or false: Across both weeks of Reaction Kinetics, to determine both the reaction order with respect to crystal violet and the reaction rate constant, we are using two independent analytical methods: the method of initial rates (in week 2/RK2) and the method of integrated rate laws.

Select one:

True

False

True

Only two of the reaction samples' crystal violet concentrations and initial rates will need to be compared to confirm the order of reaction using the initial rates method.

Select one:

True

False

False

After adding the sodium hydroxide to a reaction sample cuvette, why is it so important to quickly mix the solution and begin taking measurements?

Select one:

Since we are using the integrated rate laws to determine the reaction order and rate constant, we need to collect the data for the entire reaction, including the first few seconds.

Since there are five reactions that we need to monitor with time, we need to move quickly in order to have enough time to collect all the measurements.

Since we are using the method of initial rates to determine the reaction order and rate constant, we need to collect data as quickly as possible to avoid losing that initial rate information.

It is not important as the rate of the reaction is slow and we will still have plenty of data to use to measure the initial rate.

Since we are using the method of initial rates to determine the reaction order and rate constant, we need to collect data as quickly as possible to avoid losing that initial rate information.

Find the page for crystal violet (listed as Gentian Violet, Pubchem CID 11057) on the PubChem database (https://pubchem.ncbi.nlm.nih.gov/). Scroll to section 13 of the page's contents ("Safety and Hazards") and look at the warnings for crystal violet.

Check all of the following GHS Hazard Statements that are listed for the compound in section 13.1.1.

Select one or more:

a. Very toxic to aquatic life (with long lasting effects)

b. May cause cancer/suspected of causing cancer

c. May be corrosive to metals

d. Harmful if swallowed

e. Catches fire spontaneously if exposed to air

f. May intensify fire; oxidizer

g. Causes serious eye damage

a. Very toxic to aquatic life (with long lasting effects)

b. May cause cancer/suspected of causing cancer

d. Harmful if swallowed

g. Causes serious eye damage

True or false: After you remove 500 uL of diluted crystal violet solution from a standard sample cuvette using a 1000-uL micropipette, it is appropriate to use the same micropipette with the same tip to transfer 500 uL of 0.100 M sodium hydroxide to the cuvette for the reaction trial.

Select one:

a. True

b. False

b. False