Homework Answers

1. Which of the following defines Hess's Law?

A. Difference of enthalpy changes for the individual steps that make up the overall reaction.

B. Product of enthalpy changes for the individual steps that make up the overall reaction.

C. Sum of enthalpy changes for the individual steps that make up the overall reaction.

D. Sum of standard enthalpy for the individual steps that make up the overall reaction.

2. Flip equations around if necessary to cancel out terms on opposite sides. This is the__step in calculating the enthalpy changes based on the discussion.

A. First

B. Second

C. Third

D. Fourth

3-7. Sequence the given steps in solving for the enthalpy of combustion by writing the number in your notebook. (1-1st step to 5-5th step).

_flip equations around if necessary to cancel out terms on opposite side.

_sum up the individual steps.

_balance the individual equation.

_if necessary, look up standard enthalpies.

_changing the equation around requires a sign change of the H of that individual step.

To analyze the alcohol content of a certain wine, a chemist needs 1.00 L of an aqueous 0.200 M K2Cr2O7 (potassium dichromate) solution. How much a solid K2Cr2O7 must be waited how to make this solution?

Describe also the laboratory procedures that the chemist must employ in preparing K2Cr2O7 solution.

1.) Calculate ΔE if 120kJ of heat energy is absorbed by the system and 40kJ of work

is done on the surroundings.

2.) Find ΔE when a gas absorbs 30kJ of hear and has 15kJ of work done on it.

3.) If the internal energy of a reaction is 480J and the system absorbs 839J of heat

from it’s surrounds,

a. Find the amount of work.

b. Is the work done by the system or work is done on the system? Explain.

Please solve it like this

1. SOLUTION (what formula you use and how you solve it)

2. SOLUTION (what formula you use and how you solve it)

3.A.SOLUTION(what formula you use and how you solve it)

B. EXPLAIN

1. A solution containing 4.50 g of a non electrolyte (i=1) dissolved in 125 g of water

freezes at -0.372ºC. Calculate the molar mass of the solute.

Step 1: First compute the molality of the freezing point equation.

Step 2. Then, from the definition of molality, compute the number of moles

solute, n(solute), in the sample.

Step 3. Solve for the molar mass.

Please solve it like this

STEP1: SOLUTION (what formula you use and how you solve it)

STEP2:; SOLUTION (what formula you use and how you solve it)

STEP3: SOLUTION (what formula you use and how you solve it)