The heat energy associated with a change in temperature that does not involve a change in phase is given by

q=msΔT

where q is heat in joules, m is mass in grams, s is specific heat in joules per gram-degree Celsius, J/(g⋅∘C), and ΔT is the temperature change in degrees Celsius. The heat energy associated with a change in phase at constant temperature is given by

q=mΔH

where q is heat in joules, m is mass in grams, and ΔH is the enthalpy in joules per gram.

Physical constants

The constants for H2O are shown here:

Specific heat of ice: sice=2.09 J/(g⋅∘C)

Specific heat of liquid water: swater=4.18 J/(g⋅∘C)

Enthalpy of fusion (H2O(s)→H2O(l)): ΔHfus=334 J/g

Enthalpy of vaporization (H2O(l)→H2O(g)): ΔHvap=2250 J/g

Part A

How much heat energy, in kilojoules, is required to convert 63.0 g of ice at −18.0 ∘C to water at 25.0 ∘C ?

Express your answer to three significant figures and include the appropriate units.

Part B

How long would it take for 1.50 mol of water at 100.0 ∘C to be converted completely into steam if heat were added at a constant rate of 15.0 J/s ?

Express your answer to three significant figures and include the appropriate units.

1.2 Which strategy is not a viable “green” option in the chemical industry?
(a) Using catalysts to reduce energy consumption
(b) Reducing the number of steps in a multistep synthesis
(c) Maximizing yield
(d) Running the reaction on a smaller scale

Why would atomic absorption spectroscopy be less sensitive to low source temperature, assuming efficient atomization?

Chloroform, CHCl3, is formed by the following reaction:

CH4(g) + 3 Cl2(g) → 3 HCl(g) + CHCl3 (g)

Determine the enthalpy change for this reaction (ΔH°rxn), using the following:

enthalpy of formation of CHCl3 (g), ΔH°f = – 103.1 kJ/mol

                                CH4(g) + 2 O2(g) → 2 H2O(l) + CO2(g)        ΔH°rxn = – 890.4 kJ/mol

                                2 HCl (g) → H2 (g) + Cl2(g)                              ΔH°rxn = + 184.6 kJ/mol

                                C (graphite) + O2(g) → CO2(g)                     ΔH°rxn = – 393.5 kJ/mol

                                H2 (g) + ½ O2(g) → H2O(l)                              ΔH°rxn = – 285.8 kJ/mol

+ 145.4 kJ

– 305.3 kJ

– 145.4 kJ

+ 305.3 kJ

– 103.1 kJ

Classify each of the following as strong electrolytes, weak electrolytes or nonelectrolytes.

The photoionization of O2 produces O2+. Would you expect higher intensity for 0-0 or 0-2 transitions?

A solution is prepared using a sodium salt of an unknown diprotic base. The unknown diprotic weak base solution will be analyzed for concentration by titration with a strong acid. The unknown is placed in an Erlenmyer flask, and small, measured volumes of a standard strong acid solution are added until the final equivalence point is reached. Then the concentration of the base is calculated fromthe known volumes, the one known concentration and stoichiometry. All solutions are kept at room temperature.

A. Before the titration starts, is the solution in the flask acidic, neutral or alkaline?

B. Write a complete ionic equation for the complete (Bronsted-Lowry) acid-base neutralization reaction of a generic weak diprotic base B^2- with hydrochloric acid.

C. List the most commonform of each solute species that is present in the reaction mixture at the final equivalence point, and label each as a strong acid, weak acid, neutral, weak base, or strong base.

D. At the final equivalence point, will the overall solution be strongly acidic, weakly acidic, neutral, weakly basic, or strongly basic?

E. List the solute species that are present when more standard is added after the final equivalence point, and label each as either a strong acid, weak acid, neutral, weak base or strong base.

F. If extra titrant is added tto the flask after the final equivalence point has been reached, will the mixture be strongly acidic, weakly acidic, neutral, weakly basic, or strongly basic?

A buffer that contains 0.16 M of a base, B and 0.27 M of its conjugate acid BH+, has a pH of 8.56. What is the pH after 0.02 mol of Ba(OH)2 are added to 0.52 L of the solution?

Determine the term symbols for :

A) 3P² , B) s¹p¹d¹ electron configuration.

C) Determine the energy free ion spectroscopic state (ground state) of a d³ species.

Describe the 13C NMR spectrum of 2-methylcyclohexanol.

The reaction between sulfur gas (S₂) and carbon (C) at high temperatures (900C) results in the formation of carbon disulfide (CS₂). The reaction is: C(s) + S₂(g) = CS₂(g). What is the concentration (in moles in reaction chamber) of CS₂(g) at equilibrium if 3.00 moles of S₂(g) and excess carbon are initially added to the 1.00 L reaction chamber? The K_eq for this reaction is 3.50.

Answer the following for the reaction:

Pb(NO3)₂(aq) + 2KCl (aq) ⟶ PbCl₂(s) + 2KNO₃(aq)

a) How many grams of PbCl2 will be formed from 50.0 mL of a 1.50 M KCl solution?

b) How many mL of a 2.00 M Pb(NO3)2 solution will react with 50.0 mL of a 1.50 M KCl solution?

Calculate the pH during the titration of 20.00 mL of 0.1000 M hydrazine, NH2NH2(aq), with 0.2000 M HBr(aq) after 3.5 mL of the acid have been added. Kb of hydrazine = 1.7 x 10-6.

I. Does the solubility of the solute increase or decrease in each of the following situations?

1. Ice is placed in a glass of cola (solute is CO2 gas).

2. Honey is dissolved in hot water instead of cold water.

3. The pressure of O2 over a solution is increased (solute is O2 gas).

II. Which of the following statements about the dilution of a solution are true?

III. In order to prevent the process of either crenation or hemolysis with red blood cells an intervenous solution concentration should be ________ to the concentration of blood.