Explore BrainMass
Share

Energetics and Thermodynamics

heat evolved during combustion of hydrogen with oxygen

The combustion of hydrogen-oxygen mixtures is used to produce very high temperatures (about 2500 degrees Celsius) needed for certain types of welding. Consider the combustion reaction to be that shown below: H2 (g) + 1/2 O2 (g) ----> H2O (g) Change in Heat (Delta H) = -241.8 kJ How much heat is evolved when a

heat evolved in the reaction of CaC2 with water

Calcium carbide (CaC2) reacts with water to form acetylene (C2H2), a gas used as a fuel in welding. CaC2 (s) + 2 H2O (l) ---> C2H2 (g) + Ca(OH)2 (s) Change in Heat (Delta H) = -128.0 kJ How many kilojoules of heat are evolved in the reaction of 3.5 kg CaC2 with 1.15 L H2O?

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

Calculate the heat of dissolution (q) of urea using the following formula

Lab Questions: 1. Calculate the heat of dissolution (q) of urea using the following formula: q = -s m? Where is the heat capacity (assume the heat capacity is equivalent to the heat capacity of water: 4.184 J g-l degrees C-1, m is the mass of the solution and ?T is the change in temperature. 2. Calculate the molar enthalp

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

Thermodynamics: Enthalpy and Entropy

1. Given that a formation of a bond between two atoms is exothermic and accompanied by an entropy decrease, explain why all chemical compounds decompose into individual atoms if heated to a high enough temperature. 2. Is the dissolution of urea driven by enthalpy or entropy? How do you know this? Give one example of each of a

Entropy, Free Energy, Equilibrium

1. Define entropy and relate to probability of microstate formation. 2. Relate entropy and reaction spontaneity, Gibbs free energy and reaction spontaneity, and Gibbs free energy and the equilibrium constant of a reaction. 3. Calculate the entropy change within a system and determine absolute entropies. 4. In your own w

Heat of Vaporization of White Phosphorus

White phosphorus, P4, is normally a white waxy solid melting at 44 degree Celsius to a colorless liquid. The liquid has a vapor pressure of 400 mmHg at 35 degree Celsius and 760 mmHg at 280 degree Celsius. What is the heat of vaporization of this substance?

Specific Heats and Atomic Masses Using a Calorimeter

ChemLab program "specific heat" lab. Obtain 100 g shots of each: iron; copper & aluminum. Insert 150 ml of water at room temperature and heat to a final temperature of 100 degrees of celsius. Place in calorimeter and add 100 ml of water 20 degrees celsius. Measure specific heat for each metal and atomic weight. 100

Diels Alder Reactions of Cyclopentadiene

1) Why does cyclopentadiene dimerize so easily and rapidly to dicyclopentadiene? Please explain your answer. 2) Why must the distillation head temperature be maintained below 45oC suring the cracking of dicyclopentadiene? In other words, in the cracking of dicyclopentadiene, why is it necessary to distill the product very slowl

Work, Power and Enerhgy: Wind Turbines

Could you please explain what formula and step are involved and please provide (example) problem if possible? a)Assume a wind turbine with a hub 50 meters above the ground, a rotor diameter of 75 meters and a wind-conversion efficiency of 25 percent. The turbine operates in an area with an average wind-power density of 650 wa

Exothermic Reaction: Shifting Reactions

Please help with the following physical chemistry problem. Consider the exothermic reaction 2NO(g) + Br2(g) <----> 2NOBr(g). What can you do to the reaction mixture to produce more NOBr? (Choose from the following choices:) (a) Decrease T (b) Remove Br2 (c) Add Br2 (d) Add NOBr (e) Decrease P (f) Remove NO (g) Incre

Chemistry: Calculating the Final Temperature

An ice cube weighing 23.4 g at a temperature of 0.0 degrees Celsius is added to 125 mL of water at 24.9 degrees Celsius in an insulated container. After some time the ice cube will have melted, the cold and warm water will mix and reach a final temperature. Start by computing the heat required to melt the ice cube, and think a

heat required to melt an ice cube

How many kilojoules of heat are required to melt an ice cube having the dimensions 3.8 cm x 2.8 cm x 2.1 cm? The density of ice is 0.92 g/cm^3 (cubed). Refer to table: SUBSTANCE MELTING POINT,degrees Celsius Change in Heat of Fusion kJ/mol Mercury -38.9 2.30 E

Net Ionic Reactions of Metal Chlorides

Add 2 mL each of silver nitrate [AgNO3], lead nitrate [Pb(NO3)2] and mercury(I) nitrate[Hg(NO3)2] to the test tube. The chlorides formed are: AgCl, PbCl2, Hg2Cl2. The mixture of the 3 above compounds once precipitated is added water and then heated to to 70C to get [Pb(NO3)2] to disolve it back into solution. PRECIPITATION B

15 Thermodynamics Problems (Delta G, Delta S, Delta H)

1) From the following Ho and So values predict which of reactions I, II, and III would be spontaneous at 300ºC. H (kJ) S(J/K) I -5.0 -15 II -10.0 +20 III -5.0 -30 A. I B. II C. III D. I and II E. II and III 2) From the following Ho and So values predict which of reactions I, II, and

Iron-Sulfur Combination

1) What kind of substance is iron-sulfur combination before heating? 2) Why is it necessary to heat the test tube in order for a chemical reaction to occur? 3) What kind of substance is iron-sulfur combination after heating? 4) The element sodium reacts explosively with water and the element chlorine is a yellow-green p

Calculating the amount of heat transferred

Consider the following reaction: CH3OH -->CO + 2H2 Delta H= 90.7 kJ Calculate the amount of heat transferred when 49.0g of CH3OH is decomposed by this reaction at constant pressure. For a given sample of CH3OH, the enthalpy change on reaction is 16.5kJ . How many grams of hydrogen gas are produced? What is the val

Why Did I Get Strange Results With My Distillation Unknown?

I performed a lab that dealt with finding the melting point of an unknown liquid. The possible liquids are Acetone (56.5 C) Methanol (65.0 C) Ethanol (78.5 C) Isopropanol (82.4 C) Isopropyl acetate (88.8 C) Water (100 C) Toleuene (110.6) Methyl isobutyl ketone (116.9) and 2-Methoxyethanol (124.0 C). I did the distallation a

Calculate Ke of Given Substrates

1, Calculate Ke for the following (equilibrium concentrations given below substances) a) N2 (g) + O2 (g) + heat ↔ 2 NO (g) [0.13] [0.27] [0.346] b) 2 NH3 (g) ↔ N2 (g) + 3 H2 (g) + heat [0.011] [0.224]

Classic heat transfer/heat capacity problem

A 15.00 g iron block is dropped into a beaker containing 100.0 g of water at 20.00 degrees C. At equilibrium, the temperature of the water is 22.00 degrees C. What was the initial temperature of the block? c(water) = 4.180 J/g/ degrees C and c(Fe) = 0.449 J/g/ degrees C.

calculate the equilibrium constant Kp

The water - gas shift reaction plays an important role in the production of clean fuel from coal. CO(g) + H20(g) <--> CO2(g) + H2 (g) Given Data: Substance = CO(g) H20(g) CO2(g) H2(g) Delta H (KJ/Mol) -110.5 -241.8 -393.5 0 Delta S (

Chemistry Questions

1) If a system loses 300 kJ of heat at the same time that it is doing 600 kJ of work, what is the change in the internal energy of the system? 2) Which of the following equations represents a reaction that provides the heat of formation of sodium hypochlorite (NaOCl)? 3) The heat of combustion for 1 mole of carbon to ca

Hess's Law of Heat Summation

When 39.5 mL of 0.525 M (H4)(SO4) is added to 39.5 mL of 1.05 M KOH in a coffee-cup calorimeter at at 23.50 C, the temperature rises to 30.17 C. Calculate the H of this reaction (Assume that the total volume is the sum of the individual volumes and that the density and specific heat capacity of the solution are the same as for p

heat released for every 1.00 g of sucrose oxidation

determine how much heat is released for every 1.00 g of sucrose oxidized from the following: Sucrose C12H22O11 is oxidized in the body by O2 that ultimately produces CO2(g) and H2O (g) and releases 5.64 E3 kJ/mol sucrose. This is what I come up with for the balanced equation: 1 C12H22O11 (s) + 12 O2 (g) ----- 12 CO2 (

Calculate Energy Required

The specific heat of fusion of silver is 30.0 calories per gram and the specific heat of silver is 0.30 Joules per gram per degree C. Calculate the energy required to melt 5.0 moles of silver if it starts as a solid at 25 degree C below its normal melting point and is heated to exactly 0.01 Celsius degree above its normal meltin

Increase in Entropy

Thinking about entropy as disordered states, which of the following reactions would show an increase in entropy? Mark those in which entropy increases as TRUE. None of these reactions are balanced. H2 + O2 &#8594; H2O 1. True 2. False CaCO3 &#8594; CaO + CO2 1. True 2. False H2O(l) &#8594; H2O

INTERNAL ENERGY

In a particular reaction, the system does work on the surroundings and absorbs heat rom the surroundings. What is the sign of the internal energy change, ^U? A. always negative B. always positive C. positive or negative depending on the relative magnitudes of the energy transfers D. always zero

Enthalpy

The correct equation for which the enthalpy change defines the standard enthalpy of formation for C2H5OH (l) is : A. CH2 + CH2 + H2O -->CH3CH2OH B. CH3CHO + H2 -->CH3CH2OH C. 4 C + 6 H2 + O2 --> 2 CH3CH2OH D. 2C + 3H2 + 1/2 O2 -->2 C2H5OH E. 2C + 6H + O --> C2H5OH