Exam 2 chem
If you need 3.01 × 1023 molecules of sucrose, how many liters of a 4.00 molar solution would you need?
0.125 L
Which of the following would cause the worst burn?
1 gram of steam at 100°C
How many electrons are used to draw the electron-dot structure for acetylene, a covalent compound with the formula, C2H2?
10
How many grams of sugar (sucrose. are there in 5.0 liters of sugar water that has a concentration of 0.50 grams per liter of solution?
2.5 g
How many covalent bonds would the following atom usually form?
3
A walnut stuck to a pin is burned beneath a can containing 100.0 grams of water at 21°C. After the walnut has completely burned, the water's final temperature is a warmer 28°C. How much heat energy arose from the burning walnut?
3,000 joules
If the specific heat of gold is 0.13 J/(g°C., how much heat does it take to raise the temperature of a 1.0-gram piece of gold from 74°C to 99°C?
3.3 J
What is the molarity when water is added to 2 moles of sodium chloride to make 0.5 liter of solution?
4 M
What is the temperature change if you heat water from 55°C to 100°C?
45°C
If a material has a half-life of 24 hours, how long do you have to wait until the amount of radioisotope is 1/4 its original amount?
48 hours
How many molecules of sucrose are in 0.5 00L of a 2.00 molar solution of sucrose?
6.02 × 1023 molecules of sucrose
How many valence electrons does bromine (Br, atomic no. = 35. have?
7
Which of the beams is due to a high energy electron?
A
How can you tell whether a sugar solution is saturated or not?
Add more sugar. If it does not dissolve after mixing, the solution is saturated.
Which of the following elements will most likely not form an ion at all?
Ar
Which of the above liquids would most likely have the greatest capillary action?
B
Which of the beams is due to an energetic non-visible light wave?
B
Barium ions carry a 2+ charge, and nitrogen ions carry a 3-charge. What would be the chemical formula for the ionic compound barium nitride?
Ba3N2
Which of the following would have the smallest number of induced dipole-induced dipole interactions?
C6H14
List the following compounds in order of increasing boiling point: CI4, CBr4, CCl4,CF4.
CF4, CCl4, CBr4, CI4,
Why is calcium chloride, CaCl2, more effective at melting ice than sodium chloride, NaCl?
Calcium chloride produces three ion particles while sodium chloride produces only two. Greater numbers of ions are more effective at decreasing the number of water molecules entering the solid phase.
Which of the following elements will most likely form an ion with a -1 charge?
Cl
If all of the capillaries pictured above were the same size diameter, which would contain the liquid with the greatest capillary action?
D
Some people fear drinking distilled water because they have heard it leaches minerals from the body. What scientifically sound information might be offered to such a person?
Distilled water is relatively pure water, which loses its purity once it mixes with everything else in your stomach
People who work around radioactivity wear film badges to monitor the amount of radiation that reaches their bodies. These badges consist of small pieces of photographic film enclosed in a light-proof wrapper. What kind of radiation do these devices monitor?
Gamma radiation
Which of the following molecules would you expect to be the least attracted to a Na+ ion?
H3C-CH3
Which of the following describes reverse osmosis?
High pressure saltwater is forced against a semipermeable membrane and fresh water comes out.
Consider a lake that is uniformly 10°C. What happens to the oxygen-rich surface water as it cools down to 4°C?
It grows more dense and sinks towards the bottom.
What is a half-life?
It is the time it takes for 1/2 of the material to undergo radioactive decay.
There is more gold in 1 km3 of the ocean than the amount of gold mined in all of recorded history. How come we do not mine the oceans?
It is too dilute to separate. It would take too much energy. It would cost too much.
What is the compound that forms if you react potassium and sulfur?
K2S
Why are metal ores so valuable?
Metals can be efficiently extracted from them.
Why does water have a high specific heat?
Much of the added energy is required to break hydrogen bonds.
Which of the following molecules has the highest boiling point?
NH3
Which of the following elements will most likely form an ion with a +1 charge?
Na
Based on atomic size, which would you expect to be more soluble in water: helium, He, or nitrogen, N2?
Nitrogen atoms are bigger and so nitrogen molecules should be more soluble in water due to greater dipole-induced dipole attractions.
If all the molecules of a body remained part of that body, would the body have any odor?
No, because there would be no molecules traveling to our nose.
Which of the following nuclear equations correctly describes alpha emission?
None
Which of the following is NOT an ion?
O2
Which of the following is a negative ion?
O2-
What it the main difference between an ionic and a covalent bond?
One is the sharing of a pair of electrons, the other is the transfer of at least one electron.
Radium-226 is a common isotope on Earth, but has a half-life of about 1600 years. Given that Earth is some 5 billions years old, why is there any radium at all?
Radium-226 is a "daughter" isotope and the result of the radioactive decay of uranium.
What is the main difference between a soap and a detergent?
Soaps are made from fatty acids, detergents are synthetic.
How does a solute such as salt or sugar affect the melting and freezing of water?
Solutes slow the rate of ice formation.
Which of the following statements about fission is true?
The amount of energy released in the fission of large nuclei is very large.
If an atom has 104 electrons, 157 neutrons, and 104 protons, what is its approximate atomic mass?
The approximate atomic mass is 261.
The element uranium (U, atomic no. = 92. often has 146 (or more. neutrons but it will still undergo radioactive decay. Which statement might best describe why?
The attractive forces of the nucleons have a limited range. Any isolated neutron is not stable and will undergo spontaneous transformation into a proton and an electron.
Does the average distance that a neutron travels through fissionable material before escaping increase or decrease when two pieces of fissionable material are assembled into one piece? Does this assembly increase or decrease the probability of an explosion?
The average distance increases while the probability of an explosion also increases.
Where is the boiling point of water the greatest: at the bottom of a pot of water or just below the surface?
The boiling point of water is greatest where the water pressure is least, which is just below the surface
Fish don't live very long in water that has just been boiled and brought back to room temperature. Suggest why
The boiling process removes the air that was dissolved in the water. Upon cooling the water is void of its usual air content, hence, the fish drown.
Which of the following is a major disadvantage of nuclear-fission-based power plants?
The byproducts of the fission process are radioactive and have very long half-lives. The power plants are complex and there are many safety requirements to prevent contamination of the environment.
Why is it that in cold winters a tub of water placed in a farmer's canning cellar helps prevent canned food from freezing?
The continual release of energy by the freezing water keeps the temperature of the cellar from going below 0°C.
Why does evaporation cool a liquid?
The departing gas molecule takes some kinetic energy with it as it leaves the surface
A cat strolls across your back yard. An hour later, a dog with its nose to the ground follows the trail of the cat. Explain what is going on from a molecular point of view.
The dog is smelling molecules from the cat.
Why do red blood cells, which contain an aqueous solution of dissolved ions and minerals, burst when placed in fresh water?
The fresh water acts to dissolve the blood cell wall.
If you were to increase the pressure of a gas above a liquid (such as by pressing a piston above a liquid. what happens?
The gas is forced into solution and the solubility increases.
If nitrogen, N2, were pumped into your lungs at high pressure, what would happen to its solubility in your blood stream?
The greater the pressure, the greater the solubility
Why might sodium carbonate (washing soda, Na2CO3) be added to hard water to aid in cleaning?
The hard ions in the water are more attracted to the carbonate ions -2 charge.
Which of the following statements does not describe a property of water?
The hydrogens of a water molecule have a partial negative charge.
Which of the following statements best describes the role of neutrons in the nucleus?
The neutrons stabilize the nucleus by attracting protons and other neutrons.
Which of the following statements best describes why a large nucleus is more likely to undergo radioactive decay?
The nuclear forces are not as strong as the repulsive electrical forces between nucleons.
Why is it significantly less costly to purify fresh water through reverse osmosis than to purify salt water through reverse osmosis?
The osmotic pressure exerted by fresh water is less.
What happens if you were to place a concentrated solution into a bag made of a semipermeable membrane and were to then suspend it in a very dilute solution?
The size of the suspended bag would increase.
What happens to a soda can left in the freezer? Why?
The soda can puffs out and sometimes the lid pops open because water expands when it freezes.
Which of the following statements is true?
The valence electrons are only from s and p orbitals in the valence shell.
Which of the following statements is true?
The valence shell gives us the electron dot structure.
What property of half-lives makes radioactive material so problematic?
There is no known way to shorten a half-life. Radioactivity is limited by the natural decay-time to stable isotopes.
Which of the following solutions is the most dilute? 0.1 liter of water with 1 gram of sugar b.0.2 liter of water with 2 grams of sugar c.0.5 liter of water with 5 grams of sugar 1 liter of water with 10 grams of sugar
They all have the same concentration.
What is one role of unpaired valance electrons?
They take part in the formation of different types of bonds.
Antarctica, which is mostly ice, is much colder than the Arctic, which is a mixture of ice and water. Why? The liquid water of the Arctic Ocean absorbs and releases a lot of heat that keeps the temperatures in that region from fluctuating. b.The Arctic is much farther north than the Antarctic .c.The salt in the water of the Antarctic keeps the water from freezing. d.The specific heat of the ice is less than that of liquid water, which allows its temperature to change more readily.
Two of the above are reasonable
Cells at the top of a tree have a higher concentration of sugars than cells at the bottom. How might this fact assist a tree in moving water upward from its roots?
Water is pushed upwards by osmostic pressure
A saturated solution of compound X in water has a greater concentration than does a saturated solution of compound Y. Does it follow that compound X is also more soluble in water?
Yes, compound X is more soluble than is compound Y because a greater concentration in water can be obtained.
Which of the following statements about radiation is true?
Your body contains a number of radioactive isotopes
Water being purified using aluminum salts and a base is an example of
a physical separation
Which of the following might be considered a viable application of a radioactive tracer?
adding a stream of radioisotopes to waste water to examine where pollution goes when it flows into the ocean
The specific heat of a substance is the
amount of heat required to change the temperature of a given mass
Which of the following would be a negative ion with a single charge?
an atom with 11 protons and 12 electrons
Which of the following describes the reason for the following application of metals? designer jewelry
are shiny are strong but can be bent
Which of the following describes the reason for the following application of metals? structural supports for buildings
are strong but can be bent
When Po emits a beta particle, it transforms into a new element. What are the atomic number and atomic mass of this new element?
atomic number = 85; atomic mass = 218
An adhesive force is best described as _
attraction between two different molecules
An atom loses an electron to another atom. Is this an example of a physical or chemical change?
chemical change involving the formation of ions
Radioactivity is a tendency for an element or a material to
emit radiation
To predict the approximate energy release of either a fission or a fusion reaction, explain how a physicist uses a table of nuclear masses and the equation E = mc2.
find the change in mass and multiply by the speed of light squared
After a uranium fuel rod reaches the end of its fuel cycle (typically 3 years. most of its energy comes from the fissioning of plutonium because
fissionable Pu-239 is formed as the U-238 absorbs neutrons from the fissioning U-235
Which process would release energy from gold, fission or fusion? From carbon?
gold: fission; carbon: fusion
The farther apart two elements are located from each other in the periodic table, the
greater the polarity of the bond between them
The concept of a chemical bond is
how two or more atoms are held together
What is the leading cause of surface tension in water?
hydrogen bonding
Which of the following best describes ionic bonding?
one atom giving up some of its electrons to another atom
Which of the following solutions is the most dilute? one liter of water with 1 gram of sugarb. one liter of water with 2 grams of sugarc. one liter of water with 5 grams of sugard. one liter of water with 10 grams of sugare. They all have the same volume.
one liter of water with 1 gram of sugar
What is the name for the following polyatomic ion? PO43-
phosphate
A dipole is a
separation of charges
Which of the following provides the minimum amount of protection you need to block the following form of radiation? Alpha
suntan lotion
A material with a high specific heat
takes a lot of energy to change its temperature
Coal contains only minute quantities of radioactive materials, yet there is more environmental radiation surrounding a coal-fired power plant than a fission power plant. This indicates that
the coal-fired power plant contains none of the radiation it releases
What property primarily determines the effect of temperature on the solubility of gas molecules?
the kinetic energy of the gas
Dipole-induced dipole forces of attraction exist between water and gasoline, and yet these two substances do not mix because water has such a strong attraction for itself. Which of the following compounds might best help to make these two substances mix into a single liquid phase?
the molecule on the far left because the O-H bond is polar and the carbon and hydrogen bonds are nonpolar
During osmosis
the water moves into the concentrated solution faster than it leaves
If the following generic atom were to undergo ionization, what would the most likely product be?
would probably not ionize