a process or reaction which takes in heat from the surroundings is said to be
endothermic
a process or reaction which releases heat to the surroundings is said to be
exothermic
all of the statements regarding delta H are correct except
it can be called entropy change
Consider the reaction shown: C3H8+5O2--->3CO2+4H2O+488kcal. We can say this reaction is ______ and that the sign of H is_____.
exothermic; negative
Consider the reaction shown: 452kcal+4PCl5(s)-----> P4(s)+10Cl2(g). We can say this reaction is ____ and that the sign of H is____.
endothermic;positive
N2+O2----> 2NO deltaH= 43.2kcal. Based on the reaction shown, which statement is true?
43.2 kcal are consumed when 1.00 mole of O2 reacts
S+O2----> SO2 delta H= -70.8 kcal. Based on the reaction shown, which statement is true?
70.8kcal are consumed when 32.1g sulfur reacts
Consider the reaction shown: N2+O2--->2NO deltaH=43.2kcal. When 50.0g of N2 react, kcal will be
77.1; consumed
A reaction is said to be ____if the bonds formed during a reaction are stronger than the bonds broken.
exothermic
A positive value for deltaH for a chemical reaction is an indication of which of the following?
products have high potential energy,and the reaction is endothermic
When HCl(aq) and NaOH(aq) are mixed in a beaker, the beaker feels warm to the touch. What is known about the enthalpy of this reaction?
the reaction is exothermic
Consider this combination reaction: 2Mg(s)+O2(g)---> 2MgO(s) deltaH=-1204 kJ. What is the enthalpy decomposition of 1 mole of MgO(s) into Mg(s) and O2(g)?
602 kJ/mol
The enthalpy for the formation of 1 mole of NH3(aq) is -80.29 kJ/mol. What is the deltaHf for the formation of 3moles of NH3(aq)?
-240.87 kJ
How much heat is absorbed during production of 143gNO by the combination of nitrogen and oxygen
102kcal
Activation energy can best be described as
the difference in energy between reactants and the maximum energy
Reaction rates are determined by all of the following factors except
the spontaneity of the reaction
Which of the following statements can be assumed to be true about how reactions occur?
reactant particles must collide with each other
a rapid reaction is distinguished by
having a small value of activation energy
For a chemical reaction to occur, all of the following must happen except
a large enough number of collisions must occur
Which factors would decrease the rate of a reaction
lowering the temperature
Which of the following will affect all reaction rates
the temperature of the reactants, the presence of a catalyst, the concentrations of the reactants
In the reaction A+B--->AB, which of the following will NOT increase the rate?
decreasing the temperature
Which factors would increase the rate of a reaction
increasing the temperature, removing products as they are formed,adding a catalyst
Which statement best describes the way a catalyst works?
it decreases the value of Eact
When the concentration of the reactant is increased, the reaction rate
increases
When the temperature increases, the reaction rate
increases
When a gas reacts with a solid/liquid as the surface area of the solid or liquid reactant increases, the reaction rate
increases
What is a catalyst
a chemical which enhances the reaction rate without undergoing a permanent change in the reaction; lowers energy barrier, Eact decreases, rate increases
stage at which the rate of forward reaction is exactly equal to the rate of the reverse reaction
chemical equilibrium
do all concentrations remain constant at chemical equilibrium
yes
When writing a K= formula, which goes in the numerator, reactants or products?
products
What do you disregard from the chemical equation when writing the K= formulas
all pure liquids and solids
When K>1 at equilibrium, the predominant species existing in the products, so which reaction is favored?
forward
When K<1, the predominant species existing at equilibrium are the what
reactants
define dynamic equilibrium
rate of forward reaction equals rate of reverse reaction
Le Chatelier's principle
when stress is applied on a reaction at equilibrium by changing experimental conditions such as concentration, temperature, etc., the equilibrium will shift to lower the effects of changed parameter
When you increase the concentration of reactants
eq. will shift to the right, forward reaction will take place to reduce the concentration of the reactant
When you increase the concentration of the prodcuts
eq. will shift to the left, reverse reaction will take place
Catalysts don't change the eq. concentration, but is equilibrium reached faster or slower
faster
What turns blue litmus paper red
acids
what turns red litmus paper blue
bases
HClO4
perchloric acid
H2SO4
sulfuric acid
HI
hydroiodic acid
HBr
hydrobromic acids
HCl
hydrochloric acid
HNO3
nitric acids
What's a clue for remembering strong bases
look for OH