Explore BrainMass

Energetics and Thermodynamics

Chemistry Problem Set: Heat Energy and Temperature

The specific heat capacity of benzene is 1.74J/g*K. What is its molar heat capacity (Jmol*K)? What quanity of heat is required to raise the temperature of 50.00mL of water from 25.52 to 28.75C? The density of water at this temperature is 0.997 g/mL. When 108g of water at a temperature of 22.5C is mixed with 65.1g of wat

General chemistry questions

23) ....CrOsub2^- + ... OH^-...CrOsub4^2- + ...Hsub2O+ e^- When the equation for the half reaction above is balanced what is the ratio of the coefficient's OH^-: CrOsub2^-? a) 1:1 b) 2:1 c) 3:1 d) 4:1 e) 5:1 24) CuO(s) + Hsub2(g) <--- / ---> Cu(s) + Hsub2O(g) triangle H = -2.0kJ The Substances in

Gas Law Problem

Nitrogen and Hydrogen gases react to form Ammonia. A closed, rigid cylinder contains a total of 0.750 mol of gas at 25 degrees C and 1.10 atm before the reaction takes place; the mole ratio of hydrogen to nitrogen in the cylinder is 3:2. Determine the temperature and pressure of the gas in the cylinder at the end of the reaction

Simple Entropy

Please help with the following problems. A) Define entropy. Why is entropy considered an absolute quantity? B) For each of the pairs of substances below, choose the one expected to have the greater absolute entropy. Explain your answer. Assume 1 mol of each substance. i) Cu(s) or C(graphite) at the same temperatu

Thermodynamic Data and Standard Enthalpy of Decomposition

Use thermodynamic data to calculate the standard enthalpy of decomposition of liquid hydrogen peroxide into water and oxygen gas: H2O2(l)-->H2O(g) + 1/2 O2(g). Calculate the energy released by the decomposition of 1.0 g of 90% hydrogen peroxide solution. Molar mass of hydrogen peroxide = 34.0 g/mol. Estimate the final temperat

Estimating temperature inside a cylinder of an internal combustion engine

Estimate the temperature inside a cylinder of an internal combustion engine just after the spark has ignited the fuel. You are provided with the following list of assumptions. Assume the cylinder has a volume of 10 liters. Assume that the oxidant is air containing 20% oxygen. Assume that the fuel is octane (C9H18, molar mass = 1


When an explosive is detonated inside a shell or cartridge case, the explosion effectively takes places in a closed or fixed volume container. (The chemical decomposition is fast compared to the rate at which the projectile can gain velocity.) You can make an estimate of the explosion temperature if you assume a constant volume,

Enthalpy of Formation of CaO

Calcium metal burns according to the following equation: Ca(s) + 1/2 O2(g) --> CaO (s). When 1.00 g of calcium metal is burned in a constant pressure calorimeter with a heat capacity of 15.20 kJ/K, the temperature increases by 1.04 degrees Celcius. Calculate the enthalpy of formation of calcium oxide. Compare this answer with -

A simple problem set of 10 simple, short first year problems.

4. The term proof is defined as twice the percent of volume of pure ethanol in solution. Thus a solution that is 95% ethanol by volume is 190 proof. What is the molarity of ethanol in a 92 proof ethanol water solution? (density of ethanol is .8g/cm3; mol. wt. of ethanol is 46). 6. Find the mass percent of CuSO4 in a solut

Finding maximum temperature of water when aluminum is dropped in

A piece of aluminum with a mass of 234 grams is heated to a temperature of 231 degrees Celcius and then is dropped into 123 mL of 21 degrees celcius water. If no energy is lost to the surroundings, what will be the maximum temperature reached by the water?

2 Chemistry questions

1) The Zinc in a 1.200g sample of foot powder was precipitated as ZnNH4PO4. The strong heating of the precipitate yielded 0.4089g of Zn2P2O7. Calculate the mass percent of zinc in the sample of foot powder. 2. A mixture contains only sodium chloride and potassium chloride. A 0.1586g sample mixture was dissolved in water. It t

Calculation of bond energies and enthalpies.

You may wish to review the Laws of Thermochemistry and Endothermic and Exothermic Reactions before you begin. A table of single bond energies should be used as a help (available in most general chemistry text books). Estimate the change in enthalpy, DH, for the following reaction: H2(g) + Cl2(g) --> 2 HCl(g)

Ligand binding

Could you take a look at some problems that I have answered to see if I'm in the right direction. (a) Using this plot, estimate the enthalpy and entropy of binding for each protein to DNA. (b) What is the free energy change for the binding of WT1 and EGR1 to DNA at 25oC? (a) For each of the proteins: is the binding to

What equation is needed to find temperature?

Given the moment of inertia of 12C16O is 1.457e-46kgm^2, at what temperature would the population of particles in the J=4 state be 1/8 the population of molecules in the J=0 state?

Reaction Mechanism

A reaction occurs with the following stoichiometry A + P -> AP The concentration of A was measured versus time after mixing, the data are the following: [A](nM) Time (s) 50 0 40 100 30 229 20 411 10

Reaction Mechanisms

The reaction of a hyrogrn halide A with an olefin B to give product P according to the stoichiometric relationship: A + B -> P is proposed to occur by the following mechanism: 2A <-> A2 (fast to equilibrium) A + B <-> C (fast to equilibrium) A2 + C -> P + 2A (slow) (a) Based on this mechan

How many kilometers can you walk after eating 120 g of glucose ?

The enthalpy change involved in the oxidation of Glucose is -2880 kJ/mol. 25 % of the energy is available for muscular work. If 100 kJ of muscular work is needed to walk one kilometer, what is the maximum distance that a person will be able to walk after eating 120 g of glucose ?

Entropy for reaction

Calculate "delta" S for the following reaction: H2(g) + Br2(l) --> 2HBr(g) given: S[H2(g)] = 0.131 kJ/K S[Br2(l)] = 0.152 kJ/K S[HBr(g)] = 0.199kJ/K a. 0.482 kJ/K b. 0.681 kJ/K c. 0.115 kJ/K d. -0.084 kJ/K e. 0.084 kJ/K

The relationship between delta S and G

Predict the signs of delta S and delta H for the melting of ice at 300K? a. Delta H > 0 and delta S > 0 b. Delta H > 0 and delta S < 0 c. Delta H < 0 and delta S > 0 d. Delta H < 0 and delta S < 0 e. Not enough information provided to answer question

Calculating delta S

Calculate "delta" S for the following reaction: H2(g) + Br2(l) --> 2HBr(g) Given: S[H2(g)] = 0.131 kJ/K S[Br2(l)] = 0.152 kJ/K S[HBr(g)] = 0.199kJ/K a. 0.482 kJ/K b. 0.681 kJ/K c. 0.115 kJ/K d. -0.084 kJ/K e. 0.084 kJ/K

Gibbs free energy

Which of the following are conditions for the standard Gibbs free energy? a. Ions or molecules in solution are present at one molar concentrations b. the temperature of the system is at 298K c. gases are present at one atmosphere partial pressure d. answers a and c are correct e. answers a, b, and c are corre

Entropy and Combustion of Hydrogen Gas

Which of the following is true for the combustion of hydrogen gas? a. "change in" H > 0 b. "change in" H < 0 c. "change in" S > 0 d. "change in" G > 0 at 300K e. "change in" G > 0 at all temperatures

Entropy, enthalpy and the freezing of water

Which of the following is true for the freezing of water at 298K? a. "change in" H < 0 b. "change in" H > 0 c. "change in" S = 0 d. "change in" S > 0 e. both answers a and d are correct

Entropy, Matter and Temperatures

Which of these statements is false? a. For a given material, a gas would have a greater entropy than the solid. b. For a given material, a liquid would have a greater entropy than the gas. c. At 0 K, an ordered pure crystalline solid has an entropy of zero. d. For a given material, the liquid has a greater entropy than the


If "change in" G > 0, then a. K=0 b. K>0 c. K<0 d. K>1 e. K<1