Chemistry Practice Midterm Part 1

1. Which of the following is not a step of the scientific method?

Hypothesis

Conclusion

Observations

Graphing

The four main steps to the scientific method are observations, hypothesis, experiment, and conclusion

Explanation

The four main steps to the scientific method are observations, hypothesis, experiment, and conclusion

2. Which of the following are quantitative measurements?

Color

Mass

Texture

Odor

Quantitative observations describe a measurement. Examples: length, mass, temperature, time, ...

Explanation

Quantitative observations describe a measurement. Examples: length, mass, temperature, time, ...

3. What do the joules measure?

Atomic radius

Energy

Wavelength

Frequency

Joules are the SI unit for Energy.

Explanation

Joules are the SI unit for Energy.

4. What is the goal of the scientific method?

To prove the hypothesis correct.

To find a conclusion that you want.

To explore and test a hypothesis in order to find a conclusion.

To create a new theory.

The intent of the scientific method is never to prove a hypothesis right, but rather to explore and test a hypothesis to find a conclusion.

Explanation

The intent of the scientific method is never to prove a hypothesis right, but rather to explore and test a hypothesis to find a conclusion.

5. Which branch of chemistry focuses on compounds with carbon?

Inorganic

Organic

Analytical

Biochemistry

Inorganic deals with substances without carbon. Analytical chemistry focuses on analyzing components of compounds. Biochemistry is the study of chemistry in living organisms. Organic chemistry is focuses on compounds with carbon.

Explanation

Inorganic deals with substances without carbon. Analytical chemistry focuses on analyzing components of compounds. Biochemistry is the study of chemistry in living organisms. Organic chemistry is focuses on compounds with carbon.

6. Which of the following are a qualitative observation?

Temperature

Time

Volume

Color

Qualitative observations describe things using the senses. Examples: color, odor, and other visual descriptions.

Explanation

Qualitative observations describe things using the senses. Examples: color, odor, and other visual descriptions.

7. How many significant figures are in the following number: 4500

1

2

3

4

Significant figures include numbers 1-9 and zeros in between these numbers. Zeros at the end (right) of a number with a decimal point are significant and show precision. Placeholder zeros (left) of a number are not significant and can be rewritten in scientific notation without them. Finally, zeros at the end of a number without a decimal point do not show precision and are not significant

Explanation

Significant figures include numbers 1-9 and zeros in between these numbers. Zeros at the end (right) of a number with a decimal point are significant and show precision. Placeholder zeros (left) of a number are not significant and can be rewritten in scientific notation without them. Finally, zeros at the end of a number without a decimal point do not show precision and are not significant

8. What is the SI for frequency?

Meters

Joules

Seconds

Hertz

Frequency is the number of waves per second. Per second (s^-1) is the same as hertz.

Explanation

Frequency is the number of waves per second. Per second (s^-1) is the same as hertz.

9. How many significant figures are in the following number:0.002400500

9

8

7

6

Significant figures include numbers 1-9 and zeros in between these numbers. Zeros at the end (right) of a number with a decimal point are significant and show precision. Placeholder zeros (left) of a number are not significant and can be rewritten in scientific notation without them. Finally, zeros at the end of a number without a decimal point do not show precision and are not significant.

Explanation

Significant figures include numbers 1-9 and zeros in between these numbers. Zeros at the end (right) of a number with a decimal point are significant and show precision. Placeholder zeros (left) of a number are not significant and can be rewritten in scientific notation without them. Finally, zeros at the end of a number without a decimal point do not show precision and are not significant.

10. What is sublimation?

The process of a liquid becoming a gas.

The process of a solid becoming a gas.

The process of a solid becoming a liquid.

The process of a liquid becoming a solid.

Sublimation is the phase change of a solid becoming a gas. At the right temperature a solid mixture may be separated using sublimation.

Explanation

Sublimation is the phase change of a solid becoming a gas. At the right temperature a solid mixture may be separated using sublimation.

11. Which of the following are a heterogeneous mixture?

Carbon dioxide

Salt water

Tin

Salad

Heterogeneous mixtures are physical mixtures in which the substances do not blend well and retain their individual properties. Examples: salad, vegetable soup , sand and water, ...

Explanation

Heterogeneous mixtures are physical mixtures in which the substances do not blend well and retain their individual properties. Examples: salad, vegetable soup , sand and water, ...

12. Covert 4.0 x 10³ kilometers to millimeters

4.0 x 10^3 mm

4.0 mm

4.0 x 10^9 mm

4.0 x 10^-3 mm

(4.0 x 10^3)*(1 x 10^3)*(1 x 10^3)= 4.0 x 10^9

Explanation

(4.0 x 10^3)*(1 x 10^3)*(1 x 10^3)= 4.0 x 10^9

13. Which of the following is correct about ozone?

It shields plants and animals from harmful UV rays.

It is located in the stratosphere.

It is made around the equator.

All of the above is correct.

All of the options are correct. Ozone is the Earth's protective layer formed around the equator in the stratosphere and moves towards the poles as new ozone is formed.

Explanation

All of the options are correct. Ozone is the Earth's protective layer formed around the equator in the stratosphere and moves towards the poles as new ozone is formed.

14. Which of the following separation techniques is used to separate a heterogeneous mixture?

Crystallization

Distillation

Chromatography

Filtration

Crystallization separates a homogeneous mixture by allowing a crystal to form and remove a solid from a liquid. Distillation separates a homogeneous mixtures based on the differences of boiling points. Chromatography separates homogenous mixtures based on a substance's attraction and movement across a material. Filtration separates heterogeneous mixtures with the use of a porous barrier.

Explanation

Crystallization separates a homogeneous mixture by allowing a crystal to form and remove a solid from a liquid. Distillation separates a homogeneous mixtures based on the differences of boiling points. Chromatography separates homogenous mixtures based on a substance's attraction and movement across a material. Filtration separates heterogeneous mixtures with the use of a porous barrier.

15. Which of the following are chemical changes?

An explosion

Iron rusting.

Frying an egg.

All the above are chemical changes.

Chemical changes change the composition of a substance. Examples: rot, tarnish, rust, decompose, explode, burn,...

Explanation

Chemical changes change the composition of a substance. Examples: rot, tarnish, rust, decompose, explode, burn,...

16. What was discovered from the cathode ray tube?

Protons

Electrons

Neutrons

Atoms

The cathode ray tube is a vacuum tube with electrodes that when hooked up to electricity form a cathode ray. The cathode ray is composed of electrons and is negatively charged.

Explanation

The cathode ray tube is a vacuum tube with electrodes that when hooked up to electricity form a cathode ray. The cathode ray is composed of electrons and is negatively charged.

17. What is the octet rule?

An atom will gain, lose or share electrons to achieve 8 valence electrons.

The maximum number of valence electrons an atom can have is 8.

Chemical properties repeat every 8 elements.

None of the above are correct.

The octet rule describes how atoms will gain, lose or share electrons in order to have a complete outer valence shell (8 valence electrons)

Explanation

The octet rule describes how atoms will gain, lose or share electrons in order to have a complete outer valence shell (8 valence electrons)

18. Which relationship is true?

Wavelength increases as frequency decreases.

Wavelength increases as frequency increases.

Energy increases as frequency decreases.

Energy decreases as wavelength decreases.

E=hv and c=λν. E= energy, v= frequency, c= speed of light (constant), h = Planck's constant. Energy and frequency have a direct relationship. Wavelength and frequency have an indirect relationship. Energy and wavelength have an indirect relationship.

Explanation

E=hv and c=λν. E= energy, v= frequency, c= speed of light (constant), h = Planck's constant. Energy and frequency have a direct relationship. Wavelength and frequency have an indirect relationship. Energy and wavelength have an indirect relationship.

19. Which of the following is not true about the rules of graphing?

The independent variable goes on the x axis.

The dependent variable goes on the x axis.

Titles should be written as y vs. x.

The dependent variable is on the y axis.

When graphing the independent variable is always plotted and labeled from the x axis (horizontal). The dependent variable is located on the y (vertical) axis. Titles should always be written as y vs. x or dependent variable vs. independent variable.

Explanation

When graphing the independent variable is always plotted and labeled from the x axis (horizontal). The dependent variable is located on the y (vertical) axis. Titles should always be written as y vs. x or dependent variable vs. independent variable.

20. What ratio makes an atom neutral?

1:1 ratio of protons to neutrons

1:1 ratio of electrons to neutrons

1:1 ratio of protons to electrons

None of these. It depends upon the protons only.

Protons are positively charged and electrons are negatively charged. Neutrons are neutral. Therefore the ratio between electrons and protons must be equal in order for the charge of an atom to be neutral.

Explanation

Protons are positively charged and electrons are negatively charged. Neutrons are neutral. Therefore the ratio between electrons and protons must be equal in order for the charge of an atom to be neutral.

21. What are isotopes?

A charged atom that has gained or lost an electron.

An atom that has a different number of protons.

An atom that has a different number of neutrons.

An atom that has a different number of electrons.

Isotopes are different versions of the same element. The number of protons are the same but the number of neutrons are different. Isotopes will have the same atomic number but different mass numbers.

Explanation

Isotopes are different versions of the same element. The number of protons are the same but the number of neutrons are different. Isotopes will have the same atomic number but different mass numbers.

22. Which of the following is an intensive property?

Volume

Density

Mass

Length

An intensive property is a physical property that is not dependent on the amount of that substance. Examples: color, boiling pt., freezing pt., density....

Explanation

An intensive property is a physical property that is not dependent on the amount of that substance. Examples: color, boiling pt., freezing pt., density....

23. What is an extensive property?

A form of qualitative data.

A property that depends upon the amount of a substance.

A property that doesn't depend upon the amount of a substance.

A chemical property that depends upon an external variable.

An extensive physical property depends upon the amount of a substance. For example: volume, mass, and length.

Explanation

An extensive physical property depends upon the amount of a substance. For example: volume, mass, and length.

24. Which of the following are a physical changes?

Leaves changing colors in the fall.

Dry ice subliming into CO2.

Copper turning green in moist air.

Fruit ripening.

Physical changes are changes that do not change the composition of a substance. Dry ice is the solid form of CO2 and subliming is a phase change. All phase changes are physical changes. Examples: boil, freeze, condense, sublime, tear, crumple, ....

Explanation

Physical changes are changes that do not change the composition of a substance. Dry ice is the solid form of CO2 and subliming is a phase change. All phase changes are physical changes. Examples: boil, freeze, condense, sublime, tear, crumple, ....

25. In an experiment a student changes the temperature of water in order to measure the solubility of salt in water at different temperatures. The temperature is raised in 5 degree increments and salt is measured and added until it no longer dissolves. What is the independent variable? Dependent variable and control (in order)?

Temperature, amount of water, amount of salt.

Amount of water, amount of salt, temperature.

Temperature, amount of salt, amount of water

Amount of salt, temperature, amount of water

The independent variable is the variable that is manipulated and controlled in the experiment. The dependent variable changes is response to the independent variable. The control is a point of reference or standard for the experiment.

Explanation

The independent variable is the variable that is manipulated and controlled in the experiment. The dependent variable changes is response to the independent variable. The control is a point of reference or standard for the experiment.

26. When recording data for a experiment or measurement you should always....

Record every value you know with certainty.

Wait to write down numbers until the calculations are finished.

Count significant digits.

Record every value you know with certainty plus one estimated digit.

One estimated digit should always be included with all measurements.

Explanation

One estimated digit should always be included with all measurements.

27. How do the properties of a compound relate to the properties of the elements that comprise it?

The properties of the individual elements do not determine the properties of the compound.

The element that is most abundant determines the properties of the compound.

The properties of the compound will that of one of the elements. We just don't know which one.

The properties of the compound do not relate to the properties of the elements that create it. For example: Water is liquid at room temperature but made from two elements that are gases at room temperature. Table salt is made of two elements, one of which reacts violently with water and the other is a poisonous gas.

Explanation

The properties of the compound do not relate to the properties of the elements that create it. For example: Water is liquid at room temperature but made from two elements that are gases at room temperature. Table salt is made of two elements, one of which reacts violently with water and the other is a poisonous gas.

28. The control in the experiment....

Is always held constant.

Is the same as the dependent variable.

Is the standard for comparison.

Is the independent variable.

The control in the experiment is the standard that the results are compared to.

Explanation

The control in the experiment is the standard that the results are compared to.

29. How many valence electrons are in the following configuration?[Ar] 4s2 3d10 4p4

2

10

4

6

Valence electrons are the outermost electrons. In this case, the number of electrons that are in the highest energy level (4) is 6.

Explanation

Valence electrons are the outermost electrons. In this case, the number of electrons that are in the highest energy level (4) is 6.

30. Which of the following is/are true?A) Negative ions gain an electron and their radius gets smaller.B) Positive ions gain an electron and their radius gets smaller.C) Negative ions gain an electron and their radius gets larger.D) Positive ions gain an electron and their radius gets larger.E) Negative ions lose an electron and their radius gets smaller.F) Positive ions lose an electron and their radius gets smaller.G) Negative ions lose an electron and their radius gets larger.H) Positive ions lose an electron and their radius gets larger.

D and E

B and G

A and H

C and F

Positive ions have lost one or more electrons. When an ion loses an electron the ion has more protons than electrons and pull the electron clouds closer to the nucleus. Negative ions have gained one or more electrons. When an ion has gained an electron, the electrons repel each other (electrostatic repulsion) and the ion gets large

Explanation

Positive ions have lost one or more electrons. When an ion loses an electron the ion has more protons than electrons and pull the electron clouds closer to the nucleus. Negative ions have gained one or more electrons. When an ion has gained an electron, the electrons repel each other (electrostatic repulsion) and the ion gets large

31. Which of the following are considered a homogeneous mixture?

Salad

Vegetable soup

Water

Alloy

Homogeneous mixtures are the same throughout but are still two or more physically different substances. Water is a compound not a mixture. Salt water is a well blended mixture of two pure substances and therefore homogeneous. An alloy is a homogeneous mixture of two solids.

Explanation

Homogeneous mixtures are the same throughout but are still two or more physically different substances. Water is a compound not a mixture. Salt water is a well blended mixture of two pure substances and therefore homogeneous. An alloy is a homogeneous mixture of two solids.

32. An experiment yields data that a solution has a density of .55 g/ml. The accepted value is .65 g/ml. What is the percent error of this density measurement?

- 10 %

.10 %

15%

-.15 %

Percent error = [(experimental value - accepted value)/accepted value] x 100%

Explanation

Percent error = [(experimental value - accepted value)/accepted value] x 100%

33. What is the correct sum of the following numbers with significant figures:12.345 + 8.67 + 31.021

52.036

52.03

52.04

52.0

52.

When adding or subtracting numbers, significant digits in the answer should reflect the least precise number that your adding/subtracting. In this case, 8.67 is the least precise number because it only has two numbers after the decimal point and not three. So the answer can only have two numbers after the decimal point.

Explanation

When adding or subtracting numbers, significant digits in the answer should reflect the least precise number that your adding/subtracting. In this case, 8.67 is the least precise number because it only has two numbers after the decimal point and not three. So the answer can only have two numbers after the decimal point.

34. What is the correct product of the following numbers with significant figures:120 x 15.64

1876.8

1877

1880

1900

When multiplying or dividing numbers the answer will have the same number of significant digits in it as the number being multiplied or divided with the least number of significant digits in it. In this case, 15.64 has 4 sig figs. 120 has only 2 sig figs. So the answer should have 2 sig figs in it.

Explanation

When multiplying or dividing numbers the answer will have the same number of significant digits in it as the number being multiplied or divided with the least number of significant digits in it. In this case, 15.64 has 4 sig figs. 120 has only 2 sig figs. So the answer should have 2 sig figs in it.

35. An experiment yields data that a solution has a density of .84 g/ml. The accepted value is .90 g/ml. What is the error of this density measurement?

.06 g/ml

- .06 g/ml

.07 g/ml

-.07 g/ml

Error = experimental value - accepted value

Explanation

Error = experimental value - accepted value

36. What ratio makes an atom most stable?

1:1 ratio of protons to neutrons

1:1 ratio of electrons to neutrons

1:1 ratio of protons to electrons

None of these. It depends upon the protons only.

The stability of an atom is dependent on the ratio of the subatomic particles in the nucleus. If the ratio between protons and neutrons is not 1:1, then the atom may undergo a nuclear reaction in order to make the nucleus more stable.

Explanation

The stability of an atom is dependent on the ratio of the subatomic particles in the nucleus. If the ratio between protons and neutrons is not 1:1, then the atom may undergo a nuclear reaction in order to make the nucleus more stable.

37. Which of the following conversions is correct?

1000 cm^3 = 1 liter

1 dm^3 = 100 ml

1 cm^3 = 100 ml

They are all incorrect.

1 cm^3 = 1 ml and 1000 ml =1 liter; therefore 1000 cm^3 = 1 liter

Explanation

1 cm^3 = 1 ml and 1000 ml =1 liter; therefore 1000 cm^3 = 1 liter

38. What is density?

The amount of matter in an object.

The amount of matter with the affect of gravity.

The amount of matter contained in mass

None of these.

Density is the amount of matter in a specific volume (mass/volume). Mass is the amount of matter in an object. Weight is the measurement of mass and the affect gravity has on it.

Explanation

Density is the amount of matter in a specific volume (mass/volume). Mass is the amount of matter in an object. Weight is the measurement of mass and the affect gravity has on it.

39. Which of the following is true about atomic emission spectra?

It shows all the colors of the rainbow and therefore all visible wavelengths.

Each element produces a unique sequence of bright lines.

It is produced when atoms absorb energy.

All of the above it correct.

Atomic emission spectra is unique to every element and can be used to identify elements. It is produced when energy is released from an atom as an electron jumps from an excited state to a ground state.

Explanation

Atomic emission spectra is unique to every element and can be used to identify elements. It is produced when energy is released from an atom as an electron jumps from an excited state to a ground state.

40. What is the product of 2.4 x 10³ cm and 4.32 x 10²m?

1.04 x 10^8 cm2

1.04 x 10^5 m2

1.04 x 10^4 m2

1.0 x 10^8 cm2

When multiplying these numbers, the units first must be the same. Once converted, the exponents in the scientific notation must be added. 4.32 x 10^2 m = 4.32 x 10^4 cm. 4.32 x 10^4 cm x 2.4 x 10^3 cm = 1.0368 x 10^8 cm2. Final answer with sig figs: 1.0 x 10^8 cm2

Explanation

When multiplying these numbers, the units first must be the same. Once converted, the exponents in the scientific notation must be added. 4.32 x 10^2 m = 4.32 x 10^4 cm. 4.32 x 10^4 cm x 2.4 x 10^3 cm = 1.0368 x 10^8 cm2. Final answer with sig figs: 1.0 x 10^8 cm2