A grain sample was found in a cave.
A grain sample was found in a cave. The amount of carbon-14 in the sample was 1/16 the amount found in a fresh sample of grain. How old was the grain in the cave? The half-life of carbon-14 is 5600 years.
Chemical Kinetics
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Reaction rate constant and kinetics
The reaction CH3CH2N02 + 0H^- -----> CH3CHN02^- + H20 has the rate r=k[CH3CH2N02][0H^-] it takes 0.5 min for one % of CH3CH2N02 to react at 25 degrees C, in the case of a solution 0.002 M in CH3CH2N02 and 0.3 M in Na0H. a) Calculate k. b) Calculate also how long it would take f
Benzyl Chloride with Solvent and Rate Limiting Step
With the starting reagents of benzyl chloride and a solvent (water), what is the rate limiting step in the solvolysis reactions: a. Solubility of the alkyl halide b. Formation of the carbocation c. Reaction of the carbocation with water d. Removal of a proton from alkyloxonium ion
Rates of Effusion
Which species, ^235(UF6) or ^238(UF6), would you expect to effuse faster through a porous membrane? How much faster, i.e. what are the relative rates of effusion?
Ratio of rates from Arrhenius equation
. Question : Two reactions have the same Arhenius frequency factor, while their energies of activation differ by 5020 Jmol-1. Calculate the ratio of their rate constants at 27degree Celsius
Rate Constant for Temperatures
As you are aware, temperature affects the rate of reactions. You have the following reaction: 2A + B = C (equilibrium is = sign). For this reaction at 25 degrees Celsius, the forward rate constant, kf, is larger than the reverse rate constant, kf (i.e., kf = 10 to the 3rd x kr). Would there be a temperature at which this re
Half-life and Periodic Trends
Because the time it takes for a reaction to actually reach equilibrium is infinite, scientists have used the estimate that after ten half-lives (or ten half-times) the reaction is completed (i.e., the reaction has reached equilibrium). Chlorine gas and solid sodium metal react to produce sodium chloride. If you place one mole
General Chemistry
Kc for the reaction below at 25°C is 4.8 x 10-6. Calculate the equilibrium concentration (mol/L) of Cl2(g) if the initial concentration of ICl(g) is 1.33 mol/L. There is no I2 or Cl2 initially present. 2ICl(g) <-> I2(g) + Cl2(g) a. 6.4 x 10-6
General Chemistry problems
1. The relationship between the rate constants for the forward and reverse reactions and the equilibrium constant for a process is K = ____________. a. kf/kr b. kfkr c. kf+kr d. kf-kr e. 1/(kfkr) 2. Consider the following equilibrium. 2 SO2(g) + O2(g) 2 SO3(g) From which of the following starting conditions would
Half-Life of Decay Process
A sample of radioactive curium was found to decay in a manner that follows a first order create reaction. After 1.00 year the activity of the sample had declined from 3012 disintegration per second (create as a concentration) to 2921 disintegration per second (treat as a concentration). What is the half-life of the decay process
Kinetics: various calculations
1) Calculate the mole fraction of methanol (CH OH) in a mixture of equal masses of methanol and water. 2) Calculate the molar concentration of chloride ions in a solution prepared by dissolving 454g of CaCl in water and diluting to 500mL. 3) At 25 degrees Celcius calcium chloride has a solubi
Solving for Activation Energy
Question: Activation Energy. Use the data below to answer the following questions about a chemical reaction. A. What is the activation energy for the chemical reaction? B. What is the value of the rate constant at 430.0 K? Temperature (Degrees°C) k (1/s) 189.7 2.52 x 10-5 198.9
Catalyst Decomposition Mechanism
Acetaldehyde can undergo catalytic decomposition according to the mechanism below: CH3CHO + I2 = CH3I + HI + CO (RDS) CH3I + HI = CH4 + I2 Use the mechanism to determine: a. the overall chemical equation b the catalyst c the intermediates d. the rate law
The Concentration-Time Equation
The first-order rate constant for the decomposition of an insecticide in water at degC is 1.45 1/yr. A quantity of this insecticide is washed into a lake on June 1, leading to a concentration of 5.0 x 10-7 g/cm3 of water. Assume that the effective temperature of the lake is degC. a. What is the concentration of the insect
Gas Laws Problems
1. How do you find the ratio of rates (in grahams law) when you only are given the molar masses? 2. How do you find the t2 when you are given P1, t1, V1, and P2, and V2?
Contaminated Water Downstream
A certain pesticide is fatal to fish fingerlings at a level of 0.5 parts per million in water. A leaking metal can containing 2.0 kg of the pesticide was dumped into a stream with a flow of 10.0 Liters per second moving at 1.9 km/hr. The container leaks pesticide at a constant rate of 5.0 mg/sec. For what distance (in km) downst
Working with the Half Life Equation
Can you please explain how we are using the half life equation in this question? to get mass in grams after 13 days. The question is as follows: Gallium-67 (t 1/2 = 78.25 hours) is used to diagnose certain tumors. If you ingest 0.055 mg of 67 GA what mass will remain in 13 days. I started out using the integrated rate
First Order Reaction
The following first order reaction is conducted in an inert liquid at 45 Celsius: N2O5 N2O4 + 1/2 O2 THE RATE CONSTANT IS K=6.2*10 XY TO -4 SXY -1 AN 80.0g SAMPLE OF N2O5 IS DISSOLVED IN THE INERT LIQUID AND ALLOWED TO DECOMPOSE AT 45 CELSIUS. 1- HOW LONG WILL IT TAKE FOR THE QUANTITY OF N2O5 TO BE REDUCED TO 2.
Law of Effusion and Molar Mass
Please explain the below problems: A polymer chemist dissolves 6.053g of poly(vinyl alcohol) in enough water to make 100.0mL of solution. At 25 C, the osmotic pressure of this solution [w/respect to pure water] is 0.272atm. What's the molar mass of the polymer sample? Ans: 5.44x10^3 ------------------- A bike tire
Specific Rate Constant
Evaluate the specific rate constant for the reaction at the temperature for which the data were obtained. The rate-law expression is rate=k[A][B]squared. A + B>>>>>> C Experiment Initial [A] Initial [B] Initial Rate of Formation of C 1 0.10 M 0.10 M
Apply steady-state approximation
Consider the following mechanism for the reaction of nitric oxide with hydrogen: 1) 2NO ----> N2O2 <---- 2) N2O2 + H2 -----> N2 + H2O2 3) H2O2 + H2 ----> 2 H2O a) apply the steady state approximation to one or more of the intermediates and thence derive the rate law for the overall reaction. B) unde
Reaction Rate and Temperature
For the reaction: C2H4(g) + H2(g)----> C2H6(g) the activation energy is 181kJ/mol. The rate constant at 1000 degrees Celsius is 1.6 x 10^3 L/mol/s. A.) at what temperature is the rate constant half its value at 1000 degrees Celsius? B.) What is the rate constant at 725 degrees Celsius?
Rate expression for Reaction
The equation for the reaction between iodide and bromate in acidic solution is 6I-(aq) + BrO3-(aq) + 6H+(aq) ---> 3I2(aq) + Br-(aq) + 3H2O The rate of the reaction is followed by measuring the appearance of I2. The following data are obtained. [I-] [BrO3-] [H+] Initial Rate (mo
zero order decomposition of HI
For the zero order decomposistion of HI on a gold surface it takes 1.0 seconds for the concentration of HI to drop from 0.335M to 0.285M. HI(g)---> 1/2H2(g)+1/2I2 I need to know what is the rate constant for the reaction, how long will it take for the concentration of a 0.650M solution to drop to 0.0100M, and what is the hal
Reaction Rate - Net Reaction and Rate Law
NO is reduced by hydrogen to give N (g) & H2O vapor. One possible mechanism to account for this reaction is: Step 1: 2NO (g)<---> N2O2 (g) Step 2: N2O2 (g) + H2 (g) --> N2O (g) + H2O (g) Step 3: N2O (g) + H2 (g) --> N2 (g) + H2O (g) Determine the net reaction, the molecularity of each step and assuming step 3 is rate li
Beta Decay: What is the Product Formed?
A 25.0 mg sample of 148/58 CE (t 1/2=48s) undergoes beta decay. After 4.50 min, how much of the original sample is left, what is the product formed and how much of the product is formed?
Oxidation Experiment
If you had the follwing two oxides: Hematite (Fe2O3), magnetite(Fe3O4) How would you conduct a simple experiment to show the different oxides of Iron? Thank you so much! PS. In my lab, we just did an experiment with AL and two different unknown Copper oxides: Cu2O and CuO. We were given one of the unknown copper oxid
Recognizing the Order of a Reaction
In the reaction 2 A + 2 B ----> C + 3 D the rate of disappearance of A is -2.2 X 10^-4 M s -1. What is the rate of formation of C? The answer states A = to 1.1 x 10^-4 M/s. What happened to the "-1" in this situation? Can these measures for rates, Ms^-1 and s-1, be used to help identify first second and third order?
Chemical Kinetics Problems
Please explain what the s-1 means in the rate constant calculation. Can you please describe in detail why this is being added on as a unit and what it is used for.
Rate of Constant
The rate constant for the reaction Cl+ Cl3CH-> HCl + CCl3 is 5.8E+7M to the negative 1 s to the negative 1 at 25 degrees C and has an activation energy of 11.0KJoule/mol. Calculate the rate constant for this reaction in the lower stratosphere where the temperature is -57 degrees C. Show all work and steps to the problem.