Explore BrainMass

Energetics and Thermodynamics

Free Energy and thermodynamics

Please help answer the following questions. See the attached file for multiple choice options. 1. Which sample of sulfur at 25°C has the greatest entropy? 2. What is the standard free energy change for the following reaction at 25°C: C(diamond) ---> C(graphite) 3. Which sample of H2O has the least entropy? 4. Which su

Specific Heat

Could you please take a look at this? I'm having trouble with #2 and #3. Thank you! Observations: #1 - Initial temperature of Iron shot (Fe) metal: 100°C Final temperature of Iron shot (Fe) metal: 28°C Initial temperature of water from calorimeter: 20°C Final water temperature from calorimeter: 28°C #2

An explanation of entropy of chemical reactions

In which of the following processes will S be positive? 1. 2H2(g) + O2(g)----> 2H2O(g) 2. SO3(g) + H2O(l)-----> H2SO4(l) 3. 2KClO3(s)----->2KCl(s) + 3O2(g) A) 2 only B) 3 only C) 1 and 3 only D) 1 only E) 1 and 2 only

Heat Capacity, Enthalpy, IM Forces and Radius of Pt Atom

1.Calculate the amount of heat that must be absorbed by 10.0 g of ice at -20 C to convert it to liquid water at 60.0 C. Given: Specific heat (ice)=2.1 J/goC Specific heat(water)=4.18 J/goC H (fus)=6.0 kJ/mol 420 J 2,900 J 6,300 J 63 kJ 7.5 J 2. The major enthalpy of Boron tribromide (BBr3) is 30.5 kJ/mol, and its norma

Calories and Diet

Please explain the relationship between calories, food, and heat by responding to the following prompts: 1. List the 'magic formula' for weight loss. List a high-calorie food and a low calorie food. Do you see a relationship between the high calorie foods and the low calorie foods (other than the number of calories?) I ca

Specific heat and homeostasis

It takes 1 calorie of heat to raise the temperature of 1 gram of water 1 degree Celsius at sea level. This is referred to as the _____ of water. a. heat of fusion b. heat of vaporization c. specific heat d. heat of transformation e. heat of homeostasis

Deciding if a Reaction is Endo- or Exothermic

Calculate the value of Delta S when 1.00 mole of ethanol is vaporized at 78.0°C and 1.00 atm. I get 110 J/K mol, but is it a negative or positive number, I want to say because of vaporization it is an endothermic response which would make the number 110 J/K mol.

Entropy Change of Fusion

Assume that the enthalpy of fusion of ice is 6020 J/mol and does not vary appreciably over the temperature range 270-290 K. If one mole of ice at O°C is melted by heat supplied from surroundings at 280 K, what is the entropy change in the surroundings, in J/K?

Chemistry: Equilibrium Concentration Sample Questions

a) What is the expression for the eqilibrium constant K in terms of the concentrations of the products and reactants for the reaction between ammonia, (NH3 (aq)) (SMALL 3), WHICH REACTS WITH WATER TO PRODUCE AMMONIUM (NH4 + (aq)) and hydroxide (OH - (aq)) ions. NH3 (aq) + H20 (l) = NH4+ (aq) + OH- (aq) the enthalpy cha


Cyclopentadienone is unstable and rapidly undergoes the Diels-Alder reaction with itself. Write the structure for this Diels-Alder addition product. The Diels-Alder addition product of the question above undergoes a fragmentation reaction on heating to produce a bicyclotrienone compound plus carbon monoxide. Suggest a struc

Gas Delivery Tube

In an experiement, the directions given emphasized that the gas delivery tube must be disconnected from the top of the condenser before removing the reaction vial from the heat source. Why is this necessary?

Entropy, Free Energy, and Equilibrium

Entropy, Free Energy, and Equilibrium: Under what conditions does a substance have a standard entropy of zero? Can a substance ever have a negative standard entropy? ( I need help with answering the following question)

Methanol: Structural Formula/Enthalpy Change Calculations, Etc.

Methanol (CH3OH) has been offered as a contender for alternative motor vehicle fuel for many years. In fact the technology of burning methanol in car engines, especially racing cars, has been use since the 1960s. Methanol (also known as wood alcohol) can be produced by the fermentation of biomass (naturally occurring organic mat

Free energy and vapor pressure

Consider the thermal decomposition of CaCO3. CaCO3(s) <--> CaO(s) + CO2(g) The equilibrium vapor pressures of CO2 are 22.6 mmHg at 700°C and 1829 mmHg at 950°C. Calculate the standard enthalpy of the reaction. I am having problems finding how to used the standard free energy formula with vapor pressure. Can you help me?

Important information about Thermochemistry problem

Consider the reaction below. N2(g) + 3 H2(g)--Δ 2 NH3(g) ΔH°rxn = -92.6 kJ/mol If 1.0 moles of N2 react with 3.0 moles of H2 to form NH3, calculate the work done (in joules) against a pressure of 1.0 atm at 29°C. In Kj and then What is ΔE for this reaction? Assume the reaction goes to completion. Im not sure how t

Calculate Heat Produced by Burning Magnesium

A 0.1203 g sample of solid magnesium is burned in a constant-volume bomb calorimeter that has a heat capacity of 1769 J/?C. The calorimeter contains exactly 261 g of water, and the temperature increases by 1.126 degrees C. Calculate the heat given off by the burning Mg, in kJ/g and in kJ/mol. I have tried -16.6 KJ/g and -386

enthalpy for the combustion of pentane

1)The combustion of pentane,C5H12, occurs via the reaction: C5H12(g)+8O2(g)>>5CO2(g)+6H2O(g) with heat of formation values given by the following table: SUBSTANCE Î"H?f(kj/mol) C5H12 (g) -35.1 CO2(g) -393.5 H2O(g) -241.8 Calculate the enthalpy for the combustion of pentane Express

Calculating Enthalpy Change for the Reaction: Example Problems

1) Calculate the enthalpy change for the reaction: P4O6(s)+2O2(g)>>P4O10(s) given the following enthalpies of reaction: P4(s)+3O2(g)>>P4O6(s) deltaH = -1640.1 kJ P4(s)+5O2(g)>>P4O10(s) deltaH = -2940.1 kJ 2) From the enthalpies of reaction: H2(g)+F2(g)>>2HF(g) deltaH = -537kJ C(s)+2F2(g)>>CF4(g) deltaH = -680kJ 2C(s


1)When a 9.55 g- sample of solid sodium hydroxide dissolves in 100.0 g of water in a coffee-cup calorimeter, the temperature rises from 23.6 C to 47.4 C . Calculate the molar enthalpy (in kJ/mol NaOH) for the solution process NaOH(s)>>Na+(aq)+OH-(aq) . Assume that the specific heat of the solution is the same as that of pure w

Thermodynamics in a Reaction for Entropy Change

Thank you so much for any help you can offer. Calculate the entropy change (J/mole.K) of the reaction. The molar entropies [S] are given in brackets after each substance. 2C2H2 (g) [200.8] + 5 O2 (g) [205.0] &#8594; 4 CO2 (g) [213.6] + 2H2O (l) [69.91]

Equilibrium Constant Calculation.

I have posted several questions that I need to understand how to work for my test. Thanks! Given the thermodynamic data in the table below, calculate the equilibrium constant for the reaction: 2SO2 (g) + O2 (g) --> 2SO3 (g) Substance deltaHf° (kJ/mol) deltaS° (J/mol K) SO2(g) -2

Thermodynamics of Glycolysis Hydrolysis

In glycolysis, the hydrolysis of phosphoenol pyruvate is thermodynamically driven by the highly exergonic enol-to-keto conversion of pyruvate. From the two half reactions shown below, what is the G° (kJ/mol) of the overall reaction? Half reactions: I. phosphoenol pyruvate + H2O → enol pyruvate + HPO42- G° = -16

Calculation of decomposition temperature of Ag2O

I do not understand how to calculate this. For the following reaction: Ag2O (s) > Ag (s) + ½O2 (g) H°f (kJ / K . mole) -31 0 0 S° (J / K . mole) 121.3 42.6 205.1 Calculate the temperature (°C) where Kp = 1.

Equilibrium Calculation and Free Energy Change

Procedure 2 Determination of Kub 1. Obtain a 250 mL Beaker from the glassware shelf and place it on the lab bench. √ 2. Add 3-5 grams of solid urea to the beaker; once again the actual amount used is less important that knowing and recording the amount used. Added 3g of urea 3. Attach a thermometer to the beaker,