Thanks Kinetics of an lodine Clock Reaction Pre-lab Questions (to get credit, wo

Question

Thanks Kinetics of an lodine Clock Reaction Pre-lab Questions (to get credit, work must be clearly shown) Due at the beginning of labName 1. (2p) Define the following terms in your own words Sec a. rate law b. activation energy 2. (1p) A color change change occurs that causes the color change? will occur in this experiment that signifies the end of a trial. What chemical 3. (2p) The same amount of thiosulfate ion is added to each trial to delay the onset of the color change. Calculate the initial molarity of $,0,2- in each trial given that each trial has 1.00 mL of 0.010 M NaS,0 and a total volume of 7.00 mL 4. (2p) Calculate the initial concentration of iodide ion in trial 2 (see data table in procedure section) after the solutions in tubes A and B are mixed (but before reaction begins). . (3p) Describe how you would prepare exactly 250.0 mL of 0.180 M K2S20, solution for use in this experiment. Assume that you have a supply of solid K,S20s, deionized water, a balance, and volumetric flasks. As part of your answer, indicate how many grams of K,S20s you need.

Explanation / Answer

1.a)

The rate law or rate equation for a chemical reaction is an equation that links the reaction rate with the concentrations or pressures of the reactants and constant parameters (normally rate coefficients and partial reaction orders). For many reactions the rate is given by a power law such as

r=k[A]x[B]y

where [A] and [B] express the concentration of the species A and B (usually in moles per liter (molarity, M)). The exponents x and y are the partial orders of reaction for A and B and the overall reaction order is the sum of the exponents. These are often positive integers, but they may also be zero, fractional, or negative. The constant k is the reaction rate constant or rate coefficient of the reaction and has units of 1/time. Its value may depend on conditions such as temperature, ionic strength, surface area of an adsorbent, or light irradiation.

1.b)

Activation energy is a concept used in chemistry that was introduced by the scientist from Sweden named “Svante Arrhenius” in 1889. Activation energy is the minimum amount of energy required by chemical reactants to undergo a chemical reaction. Activation energy is also defined as the least possible energy required to initiate a chemical reaction.
The activation energy is expressed by the symbol “Ea” and is measured in kL/mol or kcal/mol. Per Svante Arrhenius, the equation for activation energy is:

K = A x e- Ea / RT

Where, K is the coefficient of the rate of reaction

A is the frequency factor

R is the universal gas constant

T is the temperature in Kelvin and

Ea is the Activation Energy

2. In a chemical change, the properties of the chemical or substance are changed. Temperature, color, smell, and texture can all change during a chemical reaction. Think of metal rusting: the metal is usually a silver color, as it rusts (goes through a chemical reaction) it changes color to the orange brown of rust. It's indicative of the chemical formula changing during the reaction

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