Physical Science II Ch. 19-21
If it takes 436 kilojoules to break a bond, how many kilojoules are released when the same bond is formed?
436 kJ of energy is released when the bond is formed
What net effect does a chemical reaction have on a catalyst?
A catalyst is unchanged by a chemical reaction
What does a catalyst do to the energy of activation for a reaction?
A catalyst lowers the activation energy of a reaction
Why are catalysts so important to our economy?
A catalyst provides an energy efficient way to perform many reactions. Using less energy saves money
How can a solution be distinguished from a suspension?
A centrifuge can be used to determine if a mixture is a solution or a suspension because it will separate out the components of a suspension
What is the difference between a soap and a detergent?
A detergent is a synthetic soap that has a stronger grease penetration. Detergents are cheaper than soaps
What defines a material as being a mixture?
A material is a mixture if it is not made completely of the same element or compound
Is 1 mole of particles a very large number of particles or a very small number?
A mole is a very large number: 6.02 x 10^23
Why is a ruby considered to be a solution?
A ruby gemstone is considered to be a solid solution because trace quantities of red chromium compounds in aluminum oxide are distributed evenly in a homogeneous mixture
Distinguish between a solute and a solvent
A solute is the thing of lesser quantity in a solution (the thing being dissolved) A solvent is the thing of greater quantity in a solution
Why does a solution of a strong acid conduct electricity better than a solution of a weak acid having the same concentration?
A strong acid has more ions in solution and can conduct electricity better
why are exothermic reactions self-sustaining?
An exothermic reaction disperses energy, which is a favorable process. as the energy is given off, entropy increases
What naturally occurring element has been contaminating the water supply of Bangladesh?
Arsenic has been contaminating the water supply of Bangladesh
What catalyst is effective in the destruction of atmospheric ozone?
Atomic chlorine is a catalyst for the destruction of ozone
Why is it not practical to have a macroscopic sample (something large enough to see) that is 100% pure?
Atoms and molecules are very small so if one atom or molecule out of a trillion is different, then the sample is no longer pure
What is the purpose of coefficients in a chemical equation?
Coefficients are used to show the ratio in which reactants combine and products form in a chemical reaction
How does distillation separate the components of a mixture?
During distillation, one of the components of the mixture is boiled and the vapor is collected in another container
How can the components of a mixture be separated from one another?
Filtration or distillation
What is the product of the reaction between carbon dioxide and water?
H2CO3
What generally happens to the rate of a chemical reaction with increasing temperature?
Higher temperatures generally increase the rate of the reaction
How is a solution different from a suspension?
In a solution all of the components are in the same phase whereas the components in a suspension are in different phases
Is concentration typically given with the volume of solvent or the volume of solution?
Liters of solution is the typical unit of volume used for measuring the concentration of a solution
Why is treated water sprayed into the air prior to being piped to users?
Mists of water sprayed into the air before piping it to users improves the water's odor and flavor by removing unpleasant smelling volatile chemicals
What are two ways in which people disinfect water in areas where municipal treatment facilities are not available?
People disinfect their water by boiling it or adding disinfecting iodine tablets
Which reactant molecules are the first to pass over the energy barrier?
Reactant molecules that are the fastest moving are the first to pass over the activation energy barrier
Why don't all collisions between reactant molecules lead to product formation?
Reactants must collide in a certain orientation with enough energy in order to react
Is sugar a polar or nonpolar substance?
Sugar is very polar as evidenced by its great solubility in water
Why do sugar crystals dissolve faster when crushed?
The crushed sugar has more surface area of contact with the water
What does it mean to say that a solution is concentrated?
The larger quantity of solute per given volume of solvent the more concentrated a solution is
Why does the solubility of a gas solute in a liquid solvent decrease with increasing temperature?
The solubility of a gas decreases with increasing temperature because the gas molecules will have more kinetic energy and be more likely to escape from solution
Why is it important never to change a subscript in a chemical formula when balancing a chemical equation?
The subscript describes how the molecule is put together and cannot be changed or it will describe a different molecule
What happens to the volume of a sugar solution as more sugar is dissolved in it?
The volume of a sugar solution gradually increases as more sugar is dissolved in it. As you add more the beaker will get fuller.
Why is it important that a chemical equation be balanced?
There must be the same number of each atom on both sides of the equation
Water and soap are attracted to each other by what type of electrical attraction?
Water and soap are attracted to each other by strong ion-dipole attractions between each water molecule and the polar head of each soap molecule
What is the purpose of a catalytic converter?
a catalytic converter decreases pollution put out by an engine by converting the emissions to less harmful chemicals
When can a solution of a weak base be more corrosive than a solution of a strong base?
a concentrated solution of a weak base could be more corrosive than a dilute solution of a strong base
Is there any energy consumed at any time during an exothermic reaction?
a small amount of energy is required to break the chemical bonds. But in an exothermic reaction the energy released exceeds the energy consumed
When a chemical loses a hydrogen ion, is it behaving as an acid or a base?
acid
What term is used to describe the minimum amount of energy required in order for a reaction to proceed?
activation energy
What is the difference between an oxidizing agent and a reducing agent?
an oxidizing agent causes another reactant to be oxidized (lose an electron), and a reducing agent causes another reactant to be reduced (gain an electron)
What is the prime difference between a battery and a fuel cell?
batteries run down while fuel cells can keep going indefinitely so long as fuel is supplied
What are some differences between corrosion and combustion?
corrosion is the deterioration of metal by oxidation. combustion is a redox reaction between a nonmetal and oxygen
What is electrochemistry?
electrochemistry is the study of electrical energy and chemical changes
What is electrolysis, and does it differ from what goes on inside a battery?
electrolysis uses electrical energy to produce a chemical change whereas a battery uses a chemical change to produce electrical energy
what is absorbed by an endothermic reaction?
energy is absorbed by an endothermic reaction
what is released by an exothermic reaction?
energy is released by an exothermic reaction
What is always increasing?
entropy
what gas has been shown to induce a state of suspended animation in mice?
hydrogen sulfide
when an acid is dissolved in water, what ion does the water form?
hydronium ion
As energy disperses, where does it go?
it goes from areas of higher concentration to areas of lower concentration
What happens to the polarity of oxygen atoms as they transform from molecular oxygen into water molecules?
oxygen atoms gain an electron
How do humans generate the air pollutant sulfur dioxide?
the burning of fossil fuels
Which elements have the greatest tendency to behave as oxidizing agents?
the elements in the upper right of the periodic table (execept for noble gases) have the greatest tendency to behave as oxidizing agents
Why aren't atmospheric levels of carbon dioxide rising as rapidly as might be expected based on the increased of output of carbon dioxide resulting from human activities?
the ocean absorbs the CO2 where it is neutralized and is not re-released
What does the pH of a solution indicate?
the pH of a solution indicates the acidity of the solution as judged by the concentration of hydronium ions
Is water a strong acid or a weak acid?
water is a weak acid
What do we do to food molecules to obtain energy from them?
we oxidize food molecules with oxygen
What do the oxidation of zinc and the oxidation of aluminum have in common?
zinc and aluminum both form water-insoluble oxidized coats that prevent further oxidation
