Exam 3 Review
for the total energy of the system to be negative, what must be true
- w > + q
In the reaction of Carbon and Oxygen to form Carbon Dioxide what is ∆E
- ∆E system = + ∆E surroundings. This is because: The reactions are at a higher energy state than the products. When you go from a higher state to a lower state, energy flows out of the system to the surroundings.
There are __________ unhybridized p atomic orbitals in an sp2-hybridized carbon atom
1
Give the temperature and pressure for the standard state for a liquid
: 1 atmosphere and 25°C
What are the possible reactants and products of combustion reactions?
A combustion reaction always includes a hydrocarbon and oxygen as the reactants and always produces carbon dioxide and water as products.
Define limiting reagent.
A reactant that is completely consumed in a chemical reaction and limits the amount of product
According to molecular orbital theory, what is an antibonding orbital
An antibonding orbital is formed when 2 orbitals destructively interfere with one another. An antibonding orbital is usually higher in energy than the two separated atoms and has a node in the internuclear region.
Explain the difference between ΔH and DE.
Change in enthalpy ΔH only tracks the exchange of heat between a system and its surroundings. Internal energy change ΔE tracks both heat and work exchanged between a system and its surroundings.
Define chemical energy.
Chemical energy is the energy associated with the relative positions of electrons and nuclei in atoms and molecules.
Where does the energy absorbed during an endothermic reaction go?
During an endothermic reaction, the products are higher in potential energy than the reactants. The thermal (kinetic) energy absorbed during reaction is used in forming products with a higher potential energy.
Electron domains: 2
Electron geometry: linear Hybridization: sp
Electron domains: 6
Electron geometry: octahedral Hybridization: sp³d²
Electron domains: 4
Electron geometry: tetrahedral Hybridization: sp³
Electron domains: 5
Electron geometry: trigonal bipyramidal Hybridization: sp³d
Electron domains:3
Electron geometry: trigonal planar Hybridization: sp²
True or False A chemical change only occurs when two different chemicals are mixed together.
False. A chemical change occurs as the result a chemical reaction. During a reaction atoms within substances are rearranged into different combinations. The mixing of just any two chemicals may not produce a reaction.
What are state functions
Functions whose values depend on the initial and final state of the system, but not on the path followed
If the enthalpy change of a reaction in a flask is ΔH = +67 kJ, what can be said about the reaction?
Heat is transferred from the surroundings to the reaction flask.
pi bond
Occurs when orbitals overlap side by side.
Classify each of the following as a path function or a state function. work energy distance traveled enthalpy heat
State functions are: enthalpy and energy. Path functions are: work, heat, and distance travelled
When attractive forces and repulsive forces are balanced then
The atoms are at the lowest point in the potential energy curve. The atoms form a stable chemical bond.
What is the greenhouse effect?
The greenhouse effect is the heating of the Earth's atmosphere that occurs when greenhouse gasses trap some of the sunlight that penetrates the Earths atmosphere. Submit
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.
Calculate the standard enthalpy change of a reaction, formula
The sum of the change of enthalpy of the PRODUCTS - the sum of the change of the enthalpy of the REACTANTS
For NH³, what orbital is hybridized and how many electrons are in that orbital?
There are five electrons in the sp³ hybrid orbitals
Why are the standard heats of formation for elements in their most stable form assigned a value of "0"?
We can't measure absolute enthalpy, but we can measure changes in enthalpy. Assigning all elements in their most stable form a value of "0" gives us a starting point from which to measure all other enthalpy changes.
sigma bond
When orbitals overlap end to end. Two atoms can form only one sigma bond.
covalent bond
a bond formed when atoms share one or more pairs of electrons
why are actual yields usually less than theoretical yields?
all reactants are not converted to products, could be using impure reactions, could have competing side effects
When a precipitation reaction occurs, the ions that do not form the precipitate _______
are left dissolved in the solution
When attractive forces exceed repulsive forces then atoms:
are to the right of the potential energy minimum
Bond energy increases with
bond order. The higher the bond order the higher the energy
energy that is associated with the relative positions of electrons and nuclei in atoms and molecules is called
chemical energy
chemical or not. the low pH of stomach acid
chemical property
heat being given off by the burning of natural gas in a kitchen stove.
chemical property
the rusting of an iron nail left out in the rain
chemical property
If a solute produces ions when dissolved, it is called an _______because the resulting ions in solution will allow the solution to conduct electricity.
electrolyte
Describe a sigma bond.
end to end overlap of p orbitals
The melting of ice in water is
endothermic. The water absorbing heat from its surroundings
Boiling water is
endothermic. this requires a heat source to raise the water's temperature. This means it needs to absorb the heat energy.
thermal energy
energy associated with the temperature of an object
A positive ∆H signals that
heat flows into a reaction system, an endothermic reaction. An example is an instant cold pack. Two reactants are kept in separate pouches. When broken and mixed, the reactant absorb heat from the surroundings.
A negative ∆H signals that
heat flows out of the reaction system, an exothermic reaction. An example is the combustion of natural gas.
As the two atoms approach each other, the attractive forces between the atoms
increase and the potential energy decreases.
Physical properties of an ice cube?
it is hard. it is cold. it has a mass of 27.3 g.
systems tend to change in order to
lower their potiental energy
Identify what a coffee cup calorimeter measures.
measures ΔH for aqueous solutions
chlorophyll being responsible for the green color of leans
physical property.
Energy formula with wavelength
planks constant * the speed of light / wavelength
what signs represent a system that is doing work on the surroundings and gaining heat from surroundings
positive q. negative w.
All the following are state functions EXCEPT (∆E. PV. ∆H. q.)
q is a path function
Describe a π (pi) bond.
side by side overlap of p orbitals.
A single bond is a
sigma bond
A double bond is a
sigma bond and a pi bond
A triple bond is a
sigma bond and two pi bonds.
The hybridization scheme for BeF2 is __________.
sp
What is the hybridization for carbon in carbon dioxide?
sp. There are two electron domains and the electron geometry is linear.
Which of the following hybridization schemes allows for the formation of at least one π bond?
sp2
In CH2=CH2, what type of hybrid orbitals are there?
sp2. sp2 hybridisation as C is attached to 3 groups and it has 3 sigma orbitals, so 1 s orbital and 2 p orbital hybridise to form sp2 orbital. sp3 orbitals cant happen as C need to have 4 orbitals for that in the hybrid set.
The electron-group geometry of a carbon-centered compound is tetrahedral. The hybridization of the central carbon atom is
sp3
The hybridizations of nitrogen in NF3 and NH3 are __________ and __________, respectively.
sp3 , sp3
What kind of hybrid orbitals are found on the central atom in SbF₅
sp³d
The prototypical d orbital has four lobes. Which describes the shape of a four-lobed d orbital?
square planar
The higher the bond order the more
stable the molecule.
Which of the following situations is most favorable for solubility?
strong attraction of solute particles to solvent particles Submit
In solution, ______exist almost entirely as ions
strong electrolytes
Chemical properties describe
the characteristic ability of a substance to react to form new substances through a new arrangement of atoms
valence bond theory
the idea that bonds are formed when orbitals of different atoms overlap
Define heat capacity.
the quantity of heat required to change a system's temperature by 1°C
Define specific heat capacity
the quantity of heat required to raise the temperature of 1 gram of a substance by 1°C
ΔH of reaction =
the sum of ΔH breaking + the sum of ΔH forming. The final answer should be in kJ
Energy can be converted from one form to another
true
The total energy of a system remains constant
true
Energy is the capacity to do
work
The heat gained by the system from the surroundings in a process carried out at constant pressure is
∆H
Assuming no hybridization, how many bonds can be formed in a molecule with the configuration of: 2s²2p⁵
1 bond
the blending of 1 s orbital and 1 p orbital produces ___________
2 sp hybrid orbitals
What is the maximum number of bonds that can form in a molecule with a central atom containing five electrons in sp³ hybrid orbitals?
3 bonds.
The blending of one s atomic orbital and two p atomic orbitals produces __________.
3 sp2 hybrid orbitals
When four atomic orbitals are mixed to form hybrid orbitals, how many hybrid orbitals are formed?
4
The blending of of 1 s orbital and 3 p orbitals produces_________________
4 sp3 hybrid orbitals
vaporization of water
Endothermic. absorbs heat, makes you, the surroundings, cold ∆H > 0
dilution of concentrated hydrochloric acid with water
Exothermic, gives off heat. ∆H < 0
Exothermic or endothermic: Combustion of hydrocarbon
Exothermic. Gives off heat. ∆H < 0)
When an electron has to lose energy it is what type of reaction?
Exothermic. It loses energy to occupy a lower energy orbital.
What are path functions
Functions whose values depend on the path followed between initial and final states.
A chemical reaction in a beaker has a ∆H= -124 kJ. Is this hot or cold?
Hot, this is an exothermic reaction
Chemical properties of aluminum would be?
It reacts with chlorine to form aluminum chloride. In moist air it combines with oxygen to form aluminum oxide.
Which of the following statements is not true of balancing a chemical equation? (A.Subscripts in the reactants must be conversed in the products B) Coefficients are used to balance the atoms on both sides C. The law of conservation of matter must be followed D. The phases in a chemical reaction tell us the nature of the reactants and products E. All of the above statements )
Subscripts in the reactants must be conversed in the products is NOT true.
The atomic orbitals of two chlorine atoms combine to form the diatomic Cl₂ molecule. Determine the atomic orbitals that overlap to form the molecule and the symbol of the noble gas that has the same electron configuration as the electron configuration of each bonded chlorine atom
The 3p orbitals overlap. Same electron configuration as Ar. (same row)
Which one of the following statements is NOT true concerning the equation below? N₂ + 3H₂↔ 2NH₃ ∆Hr° = -460 kJ (The complete reaction of 1.0 mole of N₂ produces 460 kJ of heat. B. The complete reaction of 1.0 mole of H₂ consumes 153 kJ of heat. C. The production of 1.0 mole of ammonia is accompanied by the production of 230 kJ of heat. D. The complete reaction of 1.38 mole of hydrogen requires 0.46 mole of nitrogen. E. All of these are true statements.)
The complete reaction of 1.0 mole of H₂ consumes 153 kJ of heat. The forward reaction produces heat
Why are the halogens among the most active nonmetals?
They only need one electron to attain a noble gas configuration.
Which of the following statements is true? (A. When a metal reacts with a nonmetal, an ionic compound is formed B. A metal-nonmetal reaction can always be assumed to be oxidation-reduction C. two nonmetals can undergo an oxidation-reduction reaction D. When two nonmetals react, the compound formed is ionic E. A metal nonmetal reaction involves electron transfer)
When a metal reacts with a nonmetal, an ionic compound is formed. A metal-nonmetal reaction can always be assumed to be oxidation-reduction. two nonmetals can undergo an oxidation-reduction reaction. A metal nonmetal reaction involves electron transfer.
Which of the following statements about chemical reactions is TRUE? (A. In balancing a chemical equation, all subscripts must be conserved B. When one coefficient is doubled, he rest of the coefficients in a balanced equation must also be doubled C. The subscripts in a balanced equation tell us the number of atoms in a molecule. D. An individual coefficient in an equation is meaningless. E. The phases in a chemical reaction tell us the nature of reactions and products)
When one coefficient is doubled, he rest of the coefficients in a balanced equation must also be doubled. The subscripts in a balanced equation tell us the number of atoms in a molecule. An individual coefficient in an equation is meaningless. The phases in a chemical reaction tell us the nature of reactions and products.
When two hydrogen atoms approach one another, a covalent bond is formed due to the overlap of the 1s orbital of each hydrogen atom. The process by which a covalent bond is formed is explained with the help of the graph of potential energy versus the distance between the two atoms. Identify which of the following statements are correct. ( When two hydrogen atoms are very far apart, the potential energy approaches zero. When the potential energy is zero, a covalent bond is formed. When two hydrogen atoms that are far apart approach each other, the potential energy decreases. When the distance between two hydrogen atoms is 0.74 Å, a covalent bond is formed. At a distance of 0.50 Å the potential energy is less than that at 0.74 Å.)
When two hydrogen atoms are very far apart, the potential energy approaches zero. When two hydrogen atoms that are far apart approach each other, the potential energy decreases. When the distance between two hydrogen atoms is 0.74 Å, a covalent bond is formed.
Which of the following statements is not true? (A. When a metal reacts with a nonmetal, an ionic compound is formed B. A metal-nonmetal reaction can always be assumed to be oxidation-reduction C. two nonmetals can undergo an oxidation-reduction reaction D. When two nonmetals react, the compound formed is ionic E. A metal nonmetal reaction involves electron transfer)
When two nonmetals react, the compound formed is ionic is NOT TRUE
Physical properties are characteristics that
can be measured without changing the composition of the sample under study. The appearance, but not the composition, will change.
the ability of a drainer opener to unclog a drain with sodium hydroxide
chemical property
in a bomb calorimeter, reactions are carried out at
constant volume
Increasing bond length...
decreases the strength of the bond
The strength of the bond __________ the increase in the atomic size of the bonding atoms.
decreases with
Combustion is
exothermic, releases energy in the form of heat
Freezing water is
exothermic. This involves the surrounding environment to absorb heat from the water, which means the water itself is giving off heat.
Condensing steam
exothermic. This involves water changing it's higher-energy gaseous state to a lower energy gaseous state. To do so, water vapor must release energy.
freezing of liquid N2
gives off heat, exothermic ∆H < 0
Bond energies for forming bonds are
negative
If a solute remains as a molecule when dissolved, it is called a
nonelectrolyte
A chemical change ( A. occurs when methane gas is burned. B. occurs when paper is shredded. C. occurs when water is vaporized. D. Occurs when salt is dissolved in water. E. Occurs when powdered lemonade is stirred into water. )
occurs when methane gas is burned.
A chemical change ( A) occurs when methane gas is burned. B) occurs when paper is shredded. C) occurs when water is vaporized. D) occurs when salt is dissolved in water. E) occurs when powdered lemonade is stirred into water.)
occurs when methane gas is burned.
A physical change (A occurs when iron rusts. B occurs when sugar is heated into caramel. C occurs when glucose is converted into energy within your cells. D occurs when water is evaporated. E occurs when propane is burned for heat.)
occurs when water is evaporated.
Bond energies for breaking bonds are
positive
Which of the following is not a state function? ( A. q B. E C. H D. G E. All )
q
Evidence of a chemical change
solid formation. emission of light. gas formation. color change. odor. exothermic or endothermic.
Electrolytes are compounds that can form ions when dissolved in water. This allows the resulting solution to conduct electricity. Which of the following types of compounds dissociate to form ions when placed in water?
soluble ionic compounds, acids, and bases Submit
The hybridizations of iodine in IF3 and IF5 are __________ and __________, respectively
sp3d , sp3d2
Which orbitals overlap to form the σ bond between the sulfur and fluorine atoms in the molecule SF4?
sp3d hybrid of S and 2p of F
A solute the completely dissociates into ions is a
stronger electrolyte
∆H is
the amount of heat absorbed or evolved at constant pressure
The bond length is the distance that allows
the atomic orbitals a substantial degree of overlap to balance the forces of attraction and repulsion between the nuclei. Every bond has a unique bond length, and it depends upon the strength of the interactions between the atoms and the size of the atoms.
According to valance bond theory, the greater the overlap in orbitals, the lower
the energy and the stronger the bond. In other words, hybrid orbitals minimize the energy of the molecule by maximizing the orbital overlap in a bond.
The second law of thermodynamics states that
the entropy of the universe increases during a spontaneous process.
When repulsive forces exceed attractive forces then:
the potential energy of the atoms is positive and The atoms are to the left of the potential energy minimum
As the two atoms approach each other, the attractive forces between the atoms increase and the potential energy decreases. These changes are continuous until
the repulsion between the nuclei of two atoms is greater than the attractive forces.
In solution,______exist mostly as molecules with a small fraction existing as ions.
weak electrolytes
The First Law of Thermodynamics states that
work and heat are interconvertable energy is conserved energy cannot be created or destroyed
