1. chlorine
2. fluorine
3. neon
4. nitrogen

Correct Answer Number: 3

Explanation: The noble gases, group 8A, are the least reactive elements. Look up Neon on the periodic table and notice that it has a completely filled energy shell. When an energy shell is completely filled, the element does not form bonds with other atoms. It is inert or nonreactive. Thus Neon is a monatomic gas. Cl₂, F₂, and N₂ are diatomic gases (bond with another atom. Di means two). See Table T for the formula.

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1. 248 K
2. 298 K
3. 100 K
4. 200 K

Correct Answer Number: 2

Explanation: Change Celsius to Kelvin by adding 273.
25°C + 273 = 298 K . See table T for the formula.

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1. 12.8°C
2. 14.5°C
3. 100°C
4. 18°C

Correct Answer Number: 3

Explanation: Use Reference Table H. When the vapor pressure of water is 101.3 kPa, the temperature on Table H is 100°C. When the atmospheric pressure above a liquid equals its vapor pressure, the liquid will boil. If the vapor pressure was 50 kPa, water would boil at about 82°C.

1. decrease
2. increase
3. remain the same

Correct Answer Number: 1

Explanation: By definition, temperature is a measure of the average kinetic energy of the molecules in matter. As the temperature decreases, the average kinetic energy also decreases.

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1. sublimation
2. condensation
3. melting
4. boiling

Correct Answer Number: 1

Explanation: Sublimation means to go from the solid to gas phase (without passing through the liquid phase).

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1. gas to a liquid
2. gas to a solid
3. solid to a gas
4. solid to a liquid

Correct Answer Number: 4

Explanation: Heat of fusion is the amount of energy (joules) needed to melt 1 unit of solid mass to a liquid at constant temperature. It is measured in joules/gram. See Table B.

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1. X is 20°C and Y is 20°C
2. X is 10°C and Y is 5°C
3. X is -25°C and Y is -10°C
4. X is 25°C and Y is 30°C

Correct Answer Number: 2

Explanation: Heat flow is always from high temperature to low temperature. Watch out for negative numbers. In choice 3, Y is warmer than X and heat would flow from Y to X (not what the question asks).

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1. decreases
2. increases
3. remains the same

Correct Answer Number: 2

Explanation: See the formula on Table T, combined gas law. Since the pressure is decreased, the volume will increase. Another way to look at the problem: at constant temperature volume is inversely related to pressure (Boyle Law).

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1. 10
2. 63
3. 150
4. 630

Correct Answer Number: 4

Explanation: Use H = mcT (change in temp).
H = 15 g x 4.2 J/g°C x 10°C or 630 joules.

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1. homogeneous composition
2. maximum of two components
3. minimum of three components
4. heterogeneous composition

Correct Answer Number: 1

Explanation: By definition compounds are homogenous. They cannot be separated by physical means. A mixture (salad for example) is not homogenous.

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1. ammonia
2. aluminum
3. methane
4. methanol

Correct Answer Number: 2

Explanation: Elements cannot be decomposed into simpler substances because an element by definition is one kind of substance, one kind of atom. The other choices are compounds--composed of two or more elements.

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1. 0.035 joules
2. 0.35 joules
3. 3,500 joules
4. 35,000 joules

Correct Answer Number: 4

Explanation: See Ref. Table C--kilo means 10³ or 1000.
35 x 1000 = 35,000 joules.

1. are in constant straight-line motion
2. take the shape of the container they occupy
3. have no regular arrangement
4. have stronger forces of attraction between them

Correct Answer Number: 4

Explanation: Liquids and gases take the shape of the container they occupy and both have no regular arrangement (remember solids have a regular arrangement). Both liquids and gases have particles that are in constant straight-line motion. But liquids have a constant volume because the forces of attraction between the particles keep them together. Gases do not have a constant volume and the forces of attraction between particles are weaker.

1. SO₂
2. NH₃
3. KCl
4. KClO₃

Correct Answer Number: 1

Explanation: See Table G. Steep curves reflect the greatest effect. Solubility curves that change the least (y axis) reflect compounds for which temperature has the least effect. Notice how solubility of SO₂ decreases with an increase in temperature.

1. Its crystals are a metallic gray.
2. It dissolves in alcohol.
3. It forms a violet-colored gas.
4. It reacts with hydrogen to form a gas.

Correct Answer Number: 4

Explanation: While all the answers are true for iodine, only choice 4 describes a chemical property. The other choices are physical properties.

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1. directly proportional to the Kelvin temperature.
2. directly proportional to the Celsius temperature.
3. inversely proportional to the Kelvin temperature.
4. inversely proportional to the Celsius temperature.

Correct Answer Number: 1

Explanation: See Universal Gas Law on Table T to figure this out. If the Kelvin temperature was 50 and doubled to 100, the volume would also double. Another way to look at this: according to Charles's Law, volume of a gas is directly proportional to the Kelvin temperature.

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1. sodium sulfate
2. potassium sulfate
3. copper (II) sulfate
4. barium sulfate

Correct Answer Number: 4

Explanation: See Ref. Table F. Notice how 3 of the choices are soluble but barium sulfate is (i), nearly insoluble. Therefore it has the smallest amount of solute dissolved in solution and is the least concentrated.

1. saturated
2. unsaturated
3. concentrated
4. dilute

Correct Answer Number: 1

Explanation: Equilibrium between the dissolving rate and the crystallizing rate is achieved when a solution is saturated.

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1. The boiling point decreases and the freezing point decreases.
2. The boiling point decreases and the freezing point increases.
3. The boiling point increases and the freezing point decreases.
4. The boiling point increases and the freezing point increases.

Correct Answer Number: 3

Explanation: In winter salt is put on ice to melt it because the salt makes the ice melt at a colder (decreased) temperature. Conversely, salt raises the boiling point of water. See also related question #23, this topic)

1. 2.81 g
2. 14.1 g
3. 22.4 g
4. 63 g

Correct Answer Number: 2

Explanation: Remember at STP a mole of gas occupies 22.4 liters. Density = mass / volume
or M = D x V
Substitute: 0.63 g for mass and multiply by 22.4 L to find the answer.
0.63 g x 22.4 L = 14.1 g

1. 15 cal
2. 45 cal
3. 150 cal
4. 450 cal

Correct Answer Number: 4

Explanation: Multiply the heat of fusion (30 J/g) times the number of grams (15 g). Heat of fusion is the amount of heat needed to change a solid to a liquid at the melting point.       30 J/g x 15 g = 450 J/g

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1. 23, 352
2. 7, 000
3. 15, 813
4. 158, 130

Correct Answer Number: 4

Explanation: See Ref. Table B. The heat of vaporization for water is 2259 J/g.
Multiply heat of vaporization by the grams to find the calories absorbed in vaporizing water.
70 g x 2259 J/g = 158, 130 J.

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1. high pressure and high temperature
2. high pressure and low temperature
3. low pressure and high temperature
4. low pressure and low temperature

Correct Answer Number: 2

Explanation: Think of a can of soda. The contents are under pressure and if you shake the can before opening, the soda fizzes out all over as you open it. So the higher the pressure, the more gas or more CO₂ can be dissolved in the sugar water. Eliminate choices 3 and 4. Now focus on the temperature. Soda goes flat (loses carbonation or gas) as it warms up. Soda is usually served cold because more of the carbonation or CO₂ stays in the sugar water when the soda is cold (low temp.)

1. a substance
2. a compound
3. an element
4. a mixture

Correct Answer Number: 4

Explanation: Petroleum is not listed on the Periodic Table so it cannot be an element. A compound is composed of two or more elements with a fixed composition: petroleum does not have a fixed composition. This eliminates 2 and 3.
A substance by definition is matter that has the same properties and composition throughout. Every molecule of oxygen is identical to every other oxygen molecule. Every water molecule has the same formula: H₂O. Not true for air. Air is a mixture (not the same throughout). Tossed salad, a can of mixed nuts, and gravel are mixtures. Mixtures are made of two or more substances that do not combine chemically and do not have a fixed composition. Petroleum is a mixture.

1. 64 cm²
2. 63.9 cm²
3. 63.86 cm²
4. 63.8564 cm²

Correct Answer Number: 2

Explanation: Rule: the answer has as many significant figures as the least precise measurement. 52.6 has 3 significant figures; 1.214 has 4 significant figures. The answer can not have more than 3 significant figures. Significant figures informs the reader how precise a measurement is. For example, 80 cm tells the reader, "This measurement is correct to within one cm. It might be a bit less than 80 (79) or a bit more than 80 (81) but it is very close to 80 cm." This is okay if you are installing carpet or sewing a dress but what if you are performing heart surgery or connecting fiber optic cables for a computer? Greater precision is required for this.
     80.002 informs the reader that the measurement is within a thousandth of a cm. Could be 80.001 or 80.003. When multiplying and dividing significant figures the answer can only be as precise as the least precise measurement: if 52.6 cm is multiplied by 1.214 cm, the answer cannot be correct to .004 (Remember only 1 measurement was this precise). It is only accurate to tenths of a cm (.1).
See also question #2 and #9, this topic.

1. 0.08 cm
2. 0.080 cm
3. 800 cm
4. 8.08 cm

Correct Answer Number: 4

Explanation: Rule 1: all non zero digits are significant.
Rule 2: zero digits are significant if they are part of the measurement, not place holders. In choices 1 and 2 the zeros are place holders. The answers could be written as 8 x 10^-2 and 8.0 x 10^-2. Choice four states that a measurement is 8 cm and 8/100 cm long or accurate to hundredths of a cm.
Another way to thinks of this: choice three suggests the measurement is about 800 cm: a little more or a little less but not as accurate as choice 4 and not accurate to hundredths of a cm. See #1 and #9, this topic for another example. Check out question #1 for a neat explanation of significant figures.

1. The gas is colorless.
2. The gas is carbon dioxide.
3. When the gas is bubbled in limewater, the liquid becomes cloudy.
4. When placed in the gas, a flaming splint stops burning.

Correct Answer Number: 2

Explanation: Color, turning limewater cloudy, and inability to support combustion (cause a flame to go out) are observations. Figuring out what compound has these characteristics involves making a hunch or adding up the evidence (conclusion). Sort of like Judge Judy on TV. She listens to the facts (observations) and then decides who is at fault (conclusion). Another example: there are muddy footprints on a clean floor (observation). Figuring out who made the footprints is a conclusion. Was it the dog?

1. 8.0%
2. 10.0%
3. 15%
4. 30.0%

Correct Answer Number: 2

Explanation: Per cent of error is found by subtracting the accepted value from the calculated value, dividing by the accepted value and then multiplying by 100.
Calculated value - accepted value / accepted value x 100 =
366.9 - 333.6 / 333.6 x 100 = 33.3 / 333.6 x 100 = 10%
See #6and #13 , this topic. See also Table T.

1. 3.8 / 18.6 x 100
2. 3.8 / 14. 8 x 100
3. 14.8 / 18.6 x 100
4. 18.6 / 14.8 x 100

Correct Answer Number: 2

Explanation: Per cent of error is found by subtracting the accepted value from the calculated value, dividing by the accepted value and then multiplying by 100.
calculated value - accepted value / accepted value x 100 =
18.6 - 14.8 / 14.8 x 100 = 3.8 / 14.8 x 100
See # 4 and #13, this topic. See also Table T.

1. A-> C-> E-> B-> D->
2. E-> D-> C-> A-> B
3. C-> A-> E-> D-> B
4. C-> E-> D-> A-> B

Correct Answer Number: 3

Explanation: First pour water into a beaker and take the temperature of the water. Heat of solution will be measured by determining the change of temperature after the solute (NaOH) is added to the water (and stirred). Choices 2 and 4 do not make sense as the solute NaOH is added before the temperature of the water is taken: no change of temperature can be measured this way. Choice 1 takes the temperature of the water before it is added to the beaker. Where does the water come from? Then the final temperature is taken before the solution is stirred. This method gives inaccurate readings as the thermometer could be reading a "hot" or "cold" spot in the unstirred liquid.

1. The water lost 1360 calories of heat and the metal gained 140 calories of heat.
2. The water lost 350 calories of heat and the metal gained 350 calories of heat.
3. The water gained 1360 calories of heat and the metal lost 140 calories of heat.
4. The water gained 350 calories of heat and the metal lost 350 calories of heat.

Correct Answer Number: 4

Explanation: Heat flows from hot to cold. Since the initial temp. of the water is colder than that of the metal, the metal will lose heat while the water gains heat. Eliminate answers 1 and 2.
Amount of heat flow or H = m x change in temp
H = mass of water x 32°C - 25°C (initial water temp) or
H = 50 x 7 = 350 calories of heat gained by the water.
Heat loss must equal heat gain. Therefore the metal lost 350 cal of heat while the water gained 350 cal of heat.

1. 23 g
2. 23.0 g
3. 23.017 g
4. 23.02 g

Correct Answer Number: 4

Explanation: Rule: when adding measurements, the number of decimal places in the sum (answer) is the same as the number of decimal places in the least precise measurement. The least precise measurement was measured to hundredths of a g (12.85 and 3.38). Therefore the sum of the numbers cannot be more precise than this. Even though other measurements were taken to 0.001 or 0.0001 of a gram,
in addition and subtraction the least accurate measurement rules.

1. The temperature of the solution decreases.
2. The temperature of the solution increases.
3. The solution changes color.
4. The solution gives off a gas.

Correct Answer Number: 1

Explanation: Endothermic reactions cause heat to be absorbed. The potassium nitrate needs heat to dissolve. It takes this heat energy from the water. As the water loses heat energy, the temperature of the water decreases. Note: an exothermic reaction would do the opposite: the temperature would rise as heat was given off. See also #11 and #14, this topic.

1. The dissolving of only salt A was endothermic.
2. The dissolving of only salt B was exothermic
3. The dissolving of both salt A and salt B was endothermic.
4. The dissolving of salt A was exothermic and the dissolving of salt B was endothermic.

Correct Answer Number: 4

Explanation: First eliminate answer 3: temp. of salt A increased and temp. of salt B decreased. Both salts did not react the same way.
Exothermic reactions give off heat--this causes temperatures to rise.
Endothermic reactions absorb heat--this causes temperatures to fall.
The temperature of salt A increased (exothermic reaction) while the temperature of salt B decreased (endothermic reaction). See also #10 and #14, this topic.

1. 2.25%
2. 10.0 %
3. 20.2%
4. 24.7%

Correct Answer Number: 2

Explanation: Per cent of error is found by subtracting the accepted value from the calculated value, dividing by the accepted value and then multiplying by 100.
calculated value minus accepted value / accepted value x 100 =
Be Careful! The problem already subtracted the values and gave you the difference between the measured and accepted values. You can skip the first step.
2.25 / 22.4 x 100 = 10 x 100 or 10%
See #4 and #6, this topic.

1. The solution gives off a gas.
2. The solution changes color.
3. The temperature of the solution decreases.
4. The temperature of the solution increases.

Correct Answer Number: 3

Explanation: Endothermic reactions absorb heat. As the solid dissolves, the heat energy needed to keep the reaction going will be taken from the water. As a result, the water temperature will decrease. Hint: temperature is a measure of the average kinetic energy of the molecules. As the molecules lose energy, the temperature will drop.See also #10 and #11, this topic.

1. 27.8 g / mL
2. 6.6 g / mL
3. 3.0 g / mL
4. 3.4 g/ mL

Correct Answer Number: 4

Explanation: D = M / V . First find the volume of the object by subtracting 21.2 mL from 27.8 mL or 6.6 mL
Step 2: D = M / V       or D = 22.4 g / 6.6 mL = 3.4 g / mL See also Table T.