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Principles of Chm II
chemistry the molecular science
| Question | Answer |
|---|---|
| consider the dissolving of sugar as a simple process in which kinetis is important. list which dissolves the fastest-slowest. rock candy sugar, sugar cubes, granulated sugar, powdered sugar. | Rock candy sugar is slowest, sugar cubes is slowest, granulated sugar is fastest, powdered sugar is fastest. |
| what is chemical kinetics | is the study of the speed of reactions and the nanoscale pathways or rearrangements which atoms and molecules are transformed from reactants to products. |
| Why is chemical kinetics important | is important because knowing about kinetics enables us to control many kinds of reactions in addition to combustion. |
| why is pharmaceutical chemistry important | is important to know where a drug will react with other substances in the body and how long it will take to do so. |
| what is atmospheric chemistry | it talks about the atmospheric ozone is being depleted by choloroflurocarbons |
| what is reaction rate | is defined a the change in concentration of a reactant or product per unit time. |
| what is a homogeneous reaction | is one in which reactants and products are all in the same phase (gas or solution). |
| list the 4 factors that affect the speed of a reaction | 1. the properties of reactants and products - in particular, their molecular structure and bonding.2. the concentrations of the reactants and sometimes the products, 3. the temperature at which the reaction occurs, 4. the presence of a catalyst. |
| what is a heterogeneous reaction | it takes place at a surface - at an interface between two different phases (solid & liquids). |
| How do you determine the speed of a heterogeneous reaction | it depends on the 4 factors that affect the speed of a reaction and also on the surface where the reaction occurs (fine sugar-fast, granulated-slower). |
| what is rate | rate is the speed of any process that is expresed at which the change in some measurable quantity per unit of time. |
| give formula for reaction rate | aA + bB -----> cC + dD Rate = -1/a ^[A]/^t = -1/b ^[B]/^t = 1/c [C]/^t = 1/d [D]/^t |
| what is an average reaction rate | is a reaction rate calculated from a change inconcentration divided by a change in time. |
| what is the instanteneous reaction rate | i the rate at a particular time after a reaction has begun. |
| what is the rate law | is a mathematical equation that summarizes the relationship between reactant concentration and reaction rate.. |
| what is a rate constant | the proportionality constant, k. is independent of concentration, but it has different values at different temperatures. usually becoming larger the higher the temperature. |
| how to determine the relation between rate and concentration(the rate law) | by experiments and by measuring the initial rates. |
| what is initial rates | is the instantaneous rate determined at the very beginning of the reaction. |
| what are the units for rate | moles/liter sec or min |
| general form of the rate law for many homogeneous, but not all. | Rate = k [A]^m [B]^n....concentrations of subsstances are [A] and [B] and it may be reactants, products or catalyst. exponents n,m are usually + bu night be - or gractions. |
| what does the exponent define | it defines the order of the reaction with respect to each reactant. |
| what is an integrated rate law | expresses the time dependence of a reactant concentrations. Need the reactant concentrations as a function of time. A------->products (uses calculus) |
| what is the First-Order Reaction and show formula | Rate = - ^[A]/^t = k[A]....this can be transformed using calculus, the integrated first order rate law: In [A]t = -kt + In[A]0 |
| what is the Second-Order Reaction and show formula | Rate = k[A]^2....this can be transformed using calculus, the integrated rate law: 1/[A]t = kt + 1/[A]0 |
| What is a half-life reaction | is t 1/2...is the time required for the concentration of a reactant A to fall to one half of its initial value. That is [A]t1/2 = 1/2[A]0 |
| Review the meaning of kinetic-molecular theory | molecules are in constant motion. in a gas or liquid they bump into one another, ina solid they vibrate about specific locations. molecules also ratate, flex or vibrate around or along the bonds that hold the atoms together. |
| name the 3 important types of molecular transformations/elememtary reactions | unimolecular, bimolecular and trimolecular |
| what is unimolecular reaction | is the structure of a single particle (molecule or ion) rearranges to produce a different particle or particles. They have the 1st Order Rate Law |
| an example of unimolecular reaction | isomerization of cis-2 butene |
| what is bimolecular reaction | two particles (atoms, molecules or ions) collide and rearrange into products. new bonds may be formed. they have the 2nd Order Rate Law. |
| what is trimolecular reaction | three particles (atoms, molecules or ions) react/collide with each other. they have the 3rd Order Rate Law. But these are rare. |
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