Explore BrainMass

Energetics and Thermodynamics

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


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

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

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,

Ke for Equilibrium Concentrations

1, Calculate Ke for the following (equilibrium concentrations given below substances) a) H2 (g) + Br2 (g) ↔ 2 HBr (g) + heat [0.513] [0.62] [0.346] Ke = (0.346)^2/(0.513)(0.62) = 0.376 b) N2O4 (g) + heat ↔ 2 NO2 (g) [0.0325] [0.022] Ke = [NO2]^2/[N2O4]

Thermodynamic of cyclic process of an ideal gas

An ideal gas described by T(initial)=300K,P(initial)=1 bar and V(i)=10 L is heated at constant volume until P=10 bar.It then undergoes a reversible isothermal expansion until P=1bar.It is then restored to its original state by the extraction of heat at constant pressure. Calculate w for each step.

Review Questions for a Chemistry Final

I'm reviewing for my chemistry final and need stuff explained. Please give very in-depth explanations and answers so I can understand how to do it. Thank you! Determine the amount of heat (in kJ) given off when 1.26x10^4g of N02 are produced according to the equation; 2NO(g)+O2(g)---->2NO2(g) Change of heat=-114.6 kJmol

Aqueous Equilibria and Chemical Thermodynamics

1. Calculate the pH of a) A solution that is 0.160 M in sodium formate(NaCHO2) and 0.260 M in formic acid(HCHO2). b) A solution that is 0.210 M in pyridine(C5H5N) and 0.350 M in pyridinium chloride(C5H5NHCl). c) A solution that is made by combining 125mL of 0.050 M hydrofluoric acid with 50.0mL of 0.10 M sodium fluoride. 2

Understanding Thermodynamics and Electrochemistry

1. If the equilibrium constant for a two-electron redox reaction at 298 is 1.0×10−4, calculate the corresponding and under standard conditions. 2. A cell has a standard emf of 0.104 at 298 . What is the value of the equilibrium constant for the cell reaction if ? 3. A voltaic cell utilizes the following reaction

Finding Molar Mass Through Dumas Method

We are trying to determine the molar mass of an unknown liquid through Dumas Method: measure density (mass/volume) of its vapor at a known temperature and pressure. I am having trouble answering question 3 and question 4 as attached. 1) I did the calculations for question 3 but am really lost on whether I plugged in the r

Determining Price of Ethanol: Example Problem

I am having trouble determining what I should do in this problem. I believe I start by figuring out the combustion reactions for ethanol and octane. For ethanol I have: C2H5OH(l)+ 3O2(g) = 2CO2(g) + 3H20(l) For octane I have: C8H18(g) + 25/2 O2(g) = 8CO2(g) + 9H20 I am lost on what to do next or what I should do with t

Enthalpy / entropy / free energy

Calculate the standard reaction enthalpy, entropy and free energy at 298K for the following reactions: a) CH3OH(l) + O2 (g) → CO2 (g) + H2O(l) b) P(s,white) + O2 (g) → P4O10 (s) c) sucrose + H2O (l) → α glucose + β fructose

Gases and Equilibria

1) Consider the following reaction at 1600°C: Br2(g) &#8660; 2Br(g) When 1.05 moles of Br2 are put in a 0.980-L flask, 1.2 percent of the Br2 undergoes dissociation. Calculate the equilibrium constant for Kc for the reaction. 2) Consider the heterogeneous equilibrium process: C (s) + CO2 (g) <---> 2CO (g) At 700

Thermodynamics and pH

Please see the attached file for the fully formatted problems. 1) A quantity of 7.480g of an organic compound is dissolved in water to make 300.0 mL of solution. The solution has an osmotic pressure of 1.43 atm at 27 degrees Celsius. The analysis of this compound shows that it contains 41.8 percent C, 4.7 percent H, 37.3 pe

Fuel Efficiency : Octane versus Ethanol

If we use octane (C8 H18 ) as the representative of what is contained in gasoline, and compare it to ethanol (C2H5OH), currently a promising substitute for gasoline, what will be the energy difference on a per gram basis for the two? For the reaction of octane with oxygen to produce carbon dioxide and gaseous water, 48.1 kJ of h

Chemical Thermodynamics : Enthalpy, Entropy and Gibbs Free Energy

Consider acetic acid, CH3COOH, The active ingredient in vinegar. It is also responsible for the sour taste of wine when gets exposed to air. Bacterial oxidation turns alcohol to acid. C2H5OH (aq) +O2 &#8594; CH3COOH (aq) +H2O The following data may be useful: C2H5OH (aq): &#8710;H&#730;f = -288.3 kJ/mol

Heat of Combustion Problems

1) Calculate the heat of combustion for C2H6 from the following information: C2H4+3O2-> 2CO2+2H2O C2H4+H2->C2H6 H2+1/2O2->H2O 2) Discuss the idea that the standard of living in society might be measured in units of kJ/person available in that society. The unit itself is called energy in chemical reactions if that helps

Contract or Expanding Gases

1. A sample of N2 gas occupies 2.40 L at 20oC. If the gas is in a container that can contract or expand at constant pressure, at what temperature will the N2 occupy 4.80 L? 10oC 40oC 146oC 313oC 685oC 2. When 0.56 g of Na(s) reacts with excess F2(g) to form NaF(s), 13.8 kJ of heat is evolved at standard-state cond

Physical chemistry

I just need the calculation part done. The mass of the solutes is as follows: .502g Tris and .4999g KNO3 and .4995g Pb(NO3)2 Solution Calorimetry: Heat of Ionic Reaction Solution Calorimetry is a convenient way of experimentally determining the heat of reaction in a liquid medium. Measurements in this lab will be made

Predicting Changes in a Thermodynamic System

A) The pressure of a monoatomic ideal gas in a closed system is reversibly and isochorically (constant volume) increased. Determine whether each of the following quantities is less than, equal to, or greater than zero. ΔT ΔV w q ΔP ΔU ΔH ΔS b) A real gas is found to have a molar volume that is 90% of the

Derive and Apply Heat Capacity

Suppose that the enthalpy of some substance over a large temperature range can be expressed as a function of the temperature (where alpha, beta and gamma are constants): H =alpha*ln(T) + ln(gamma) + beta/T^2 a) What is the heat capacity of this substance at constant pressure? b) You begin with two samples each contai

Thermodynamics : Enthalpy of Formation, Heats of Reaction and Heating Curves

1.) Use the values of &#8710;Hof given below to calculate (in kJ) &#8710;Horxn for the following reaction: C2H5OH (l)+ 3O2(g) &#8594; 2CO2(g) + 3H2O(g) Given: &#8710;Hof (kJ/mol) C2H5OH (l) -278 O2(g) 0 CO2(g) -394 H2O(g) -242 2.) The graph below shows the heating curve of water. Use this graph to answer the fol

Calorimetry, Heat Capacity, Temperature Change and Changes of State

Please see the attached file for the fully formatted problem(s). Heat, Energy, and Changes of State Part A How much energy in joules would be absorbed by 3.0 L of liquid oxygen as it vaporized? The density of liquid oxygen at its boiling point is 1.14 kg/L , and its heat of vaporization is 213 kJ/kL . Express yo

Equilibrium constant

Please see the attached file for full problem descriptions: 1. A quantity of 0.20 mol of carbon dioxide was heated to a certain temperature with an excess of graphite in a closed container until the following equilibrium was reached: C (s) + CO2 (g) <--> 2CO (g) Under these conditions, the average molar mass of the gas was

the change in enthalpy and entropy

5. C(s) + CO2(g) ---> 2 CO(g) Carbon (graphite), carbon dioxide and carbon monoxide form an equilibrium mixture as represented by the equation above. (a) Predict the sign for the change in entropy, deltaS, for the reaction. Justify your prediction. (b) In the table below are data that show the percent of CO in the equi

Combustion of Pentane, Enthalpy, and Graham's Law of Diffusion

3. Consider the hydrocarbon pentane, C5H12 (molar mass 72.15 g). (a) Write the balanced equation for the combustion of pentane to yield carbon dioxide and water. (b) What volume of dry carbon dioxide, measured at 25 C and 785 mm Hg, will result from the complete combustion of 2.50 g of pentane? (c) The complete combusti

Calorimetry Lab - Enthalpy Change of a Chemical Reaction

Procedure: 1. Take a calorimeter from the glassware shelf and place it on the workbench. 2. Take a balance from the tools shelf and drop it on the calorimeter. Record the mass of the empty calorimeter. 3. Take a thermometer from the tools shelf and drop it onto the calorimeter. Record the temperature of the calorimete

Enthalpy - Dissolution of Urea Lab Project and Two Questions

Scenario: In lab, we added 4 (g) "solid" Urea CO(NH2)2 to a beaker and filled a buret with 50 ml H2O. We then attached a thermometer to the beaker. We added 1 ml of H2O from buret until "solid" Urea dissolved. We had to record the temperature with each 1 ml added. We had to repeat this experiment 2 more times using diffe