Explore BrainMass

Energetics and Thermodynamics

Gas-phase absolute entropy

1. Which molecule below should have the highest gas-phase absolute entropy at 25°C? a. CH4 b. H2 c. C2H6 d. C2H4 e. C2H2 2. Some standard entropies (at 25°C in J/mol K) are given: Ca2+(aq) -55.2, F-(aq) -9.6, CaF2(s) +68.87. ΔS° for the reaction CaF2(s)  Ca2+(aq) + 2F-(aq) at 25°C in J/K is ____

General Chemistry and Thermodynamics

7.5. Given the following table of thermodynamic data, substance ΔHf° S° POCl3 (g) -542.2 kJ/mol 325 J/mol - K POCl3 (l) -597.0 222 determine the normal boiling point (in °C) of POCl3. a. 133.0 b. 532 c. 273

General Chemistry - Law of thermodynamics

1. Which one of the following is a correct statement of the first law of thermodynamics? a. ΔS = q - T absolute zero, for a pure crystalline solid, S = O c. ΔS >or equal q/T d. ΔH = ΣΔHproducts - ΣHreactants e. ΔE = q + w 2. A reversible process is one that ________. a. must be carried out at high

Does this solution dissolve the solid?

When lithium iodide is dissolved in water, the solution becomes hot. If an aqueous solution of LiI together with additional solid LiI were heated, would some of the solid dissolve or would more solid precipitate? I am very confused as to what this means and I can't find anything that really explains it in my book.

Enthalpy Change in a Calorimeter

You mix together the following solutions in a coffee-cup calorimeter: - 100.0 mL of 0.200 M CsOH - 50.0 mL of 0.400 M HCl Both solutions start out at 22.50°C, and the final temperature after reaction is 24.28°C. The densities of the solutions are all 1.00 g/mL, and the specific heat of the mixture is 4.2 J/g°C. Calculat

Thermodynamics and Specific Heat

You are given 10.0 grams of a mixture of NaNO3 and KF. You dissolve this mixture in 100.0 grams of water, and the temperature rises by 1.02°C. Calculate the mass of each salt in the original mixture. Assume that the specific heat of the solution is 4.18 J/g°C. Useful information: Enthalpy of solution of NaNO3: +20.5 kJ/mol

Thermodynamics and Enthalpy of Formation

I need some help with this problem, see attached file for full problem description with proper symbols: 2. a) Use only the following data to determine delta H°f for NO2 (g): - delta H°f for NO (g) is +90.4 kJ/mol - delta H = -56.6 kJ/mol for the reaction: NO (g) + 1/2 O2 (g) ---> NO2 (g) b) Find delta H for the reaction: 4


1. I need help with the standard deviation/percentage error in the attached lab experiment. 2. Also need help graphing for the ethyl acelate and unknown solvent -- plotting negative delta T versus the total volume of solute that was added (2 graphs) and calculation of the slopes 3. I am not certain but I believe this ques

P chem

Calculate deltaS standard for the sublimation of CO2. The enthalpy of sublimation is delta H^0=25.23 kJ/mol at 195K. delta S^0= 1 ATM


1. In a free radical reaction, the following step would be categorized as CH3. + Br . ----------> CH3Br a. Initiation b. Propagation c. Substitution d. Termination 2. The heat of reaction (enthalpy change, delta H) for the following reaction is I2 + CH4 -----------> CH3I + HI a. 13 kcal/mol b. 140 kca

Vapor Density & Ideal Gas Law

Please take a look at the attached lab report on vapor density. Please see the ** items regarding percentage error and calculation of R. I can't figure out how to do the percentage error of my trials and the calculations for the R values are confusing. Thanks for your help. --- Vapor Density and the Ideal Gas Law Lab Con

Specific heat of iron

How much energy is required to heat a #10 iron nail with a mass of 7.0 g from 25.0 degrees celsius until it becomes red hot at 75? Please use degrees celsius. (specific heat of iron is .444 j/g degrees celsius)

State Functions

Which one is not a state function? 1. change in enthalpy 2. Work done by a system 3. (q + w) 4. Change in s (entropy) I know it is either #2 or #3, I think it is #2 but I am confused.

Energy and disorder

If 10 grams of the sugar C12H22O11 burned in a calorimeter and produced a 5.5 C temperature change in 1500 grams of water, what would be the heat of combustion of 1 mole of sugar. Choices:34.5kj/m, -34.5, 1150, -1150.

Enthalpy Change and Affecting Variables

Change in (delta) H degrees = 2816kJ 6CO2(g) + 6H2O (l) <->C6H12O6(s) + 6O2 (g) How is the equilibrium yield of C6H12O6 affected by: a. Increasing P CO2 (explain) b. Increasing temperature (explain) c. Removing CO2 (explain) d. Decreasing the total pressure (explain) e. Removing part of the C6H12O6 (explain) f. Addin

Multiple Choice Questions on heat and energy

1) The standard free engery of a reaction is related to the equilibrium constant. How many KJ/mol change is required for the equilibrium constant to change by 10 at 25 degrees? a.1.4 kj/mol b. 5.6kj/mol c.7.9kj/mol d. 18.8kj/mol 2) Which thermodynamic function depends on the path taken from state 1 to state 2? a. Interna

Basic Chemical Equations

1. a. Calculate the [H+] of a weak acid solution with [OH-] = 3.50x10^-8M b. Calculate the pH of the solution c. Calculate the [H+] of a Classic Coke if the pH=3.75 2. Write the balanced equations: (Neutralizations) in ionic form and show net ionic equation. a. H2SO4(aq) + NaHCO3(aq)--> b. H3PO4(aq)+Mg(OH)2--> 3. Cal

Heating Curve of solid subtance

In a heating curve of a solid substance: Which phase (curve) would represent the heat of vaporization? Which phase (curve) would represent kinetic energy? Which phase (curve) would represent the melting point? Which phase (curve) would represent the phase change (s)? Which phase (curve) would represent the greatest increa

Gases, Temperature, Current and Reactions

1) Calculate w and Delta E for the expansion of 20.0g of nitrogen gas from a volume of 30.0 L to a volume of 40.0 L at a constant 300.0K. 2) The density of ice at its normal freezing temperature is 0.917g/mL while that of liquid water at the same temperature is 0.9998 g/mL . If Delta H(fusion) of ice is 6.009 kJ/mol, what is

Heat energy and water

I have the data but I am having a hard time determining the end result. How much heat energy is required to raise the temp. of 5.0g of H20 from -10C to 110C ? (ice to steam) Given the following data: Specific Heat J/gK Molar Heat Capacity J/molK Formula Mass Water (l) 4.184

Heat energy and H20

How much heat energy is required to raise the temperature of 5.0g of H20 from -10 degrees celsius to 110 degrees celsius ?

Dealing with exothermic and endothermic reactions

I am in summer school and I missed both of these on my test and my final is cumulative and there will be questions like these on the final. 1. Sketch a diagram representing an exothermic reaction. Label both the horizontal and vertical axes. Show reactants and products, energy of activation and (delta Hrxn) on your sketch.

Boiling Point of Chloroform

Chloroform has a Hvap = 29.2 kJ/mol and has a Svap=87.5 J/(mol 61504;K). What is the boiling point of chloroform in Celsius?

Bromine entropy of vaporization

Hi, Please explain this as ELEMENTARY as possible. Bromine is one of the only two elements that is liquid at room temp. Bromine has a heat vap of Hvap = 30.91kJ/mol and its boiling point is 59EC. What is the entropy of vaporization for bromine?

Calculating percent yield in a reaction

A chemist ran the reaction CH3CH2Cl(l) + KOH(aq) ^ CH3CH2OH(l) +KCL(aq) by heating 47.2 grams of CH3CH2Cl with excess KOH and obtained a yield of 28.7 grams of CH3CH2OH. What was his % yield? I do not know where to begin with this problem. It only gives grams of one reactant? What is the actual yield? Detailed step by step in

How conditions alter rate of enzyme-catalyzed reaction

How will each of the following changes in condition alter the rate of an enzyme-catalyzed reaction: -decreasing temp to 10 deg C? -increasing the pH of the solution from 7 to 11? -heating only the enzyme to 100 deg C?