Assignment 1 (for credit) PDF

Preview

Summary

full online assignment you can complete before released, this is the hardest one...

Description

Assignment 1 (for credit) Due: 6:00pm on Friday, September 21, 2018 You will receive no credit for items you complete after the assignment is due. Grading Policy

I Physical properties can be classified as either intensive properties or extensive properties. An intensive property is independent of the amount of the sample. An extensive property varies with the amount of the sample.

Part A Classify the following as intensive or extensive properties of zinc. Drag the appropriate items to their respective bins. You did not open hints for this part. ANSWER:

Reset

bluish gray in color

Help

has a mass of 63.74 g

begins to melt at 419.58 degrees Celsius

has a volume of 8.94 mL

has a density of 7.13 g/mL

Part B You are given a sample resembling zinc. Which of the following properties could be used to help determine whether the sample is really zinc? Check all that apply.

Hint 1. How to approach the problem The intensive properties of a substance are characteristic of that substance and help distinguish it from other substances. Therefore, you should choose the intensive properties from the list.

ANSWER: the volume of the sample the density of the sample the melting point of the sample

Dimensional Analysis Learning Goal: To understand how to use dimensional analysis to solve problems. Typesetting math: 100%

Dimensional analysis is a useful tool for solving problems that involve unit conversions. By carefully tracking units and conversion factors, you can avoid many of the errors commonly encountered in chemistry problems. Dimensional analysis can also help you work through problems when you are not sure where to begin.

For example, dimensional analysis could be used to determine the number of nickels in 3432.35 To begin, write down the starting value, 3432.35

.

. This can also be written as a fraction:

Next, convert dollars to cents. This conversion involves a simple conversion factor:

.

. Note that the "dollar" unit should appear on the bottom of this

conversion factor, since "dollars" appears on the top of the starting value. Finally, convert cents to nickels. This conversion also involves a simple conversion factor:

. This time "cents" should be on the bottom of the conversion

factor, since it was on top of the previous conversion factor. Combining these expressions gives us

Finally, cancel units. Since dollars are divided by dollars, and cents are divided by cents, both of these units can be canceled. Multiplying through gives the final result:

To complete the calulation, multiply everything in the numerator and divide by everything in the denominator (or top and bottom, respectively). Practice with a sample problem You wash dishes for a chemistry laboratory to make extra money for laundry. You earn 12 .

, and each shift lasts 75

. Your laundry requires 12

Part A How many shifts must you work if you wish to wash 10

of laundry?

Express your answer numerically as an integer. You did not open hints for this part. ANSWER:

Part B Complete previous part(s) Part C How many loads of laundry will each shift pay for if the cost per load rises to 16

?

Express your answer numerically as an integer. You did not open hints for this part. ANSWER:

Learning Goal: To learn how to round an answer to the correct number of significant figures. When we report a measurement in science, we are careful to report only digits known with certainty, plus a final digit that is recognized to be uncertain. We call this set of digits significant figures. Often, these numbers are used in calculations. When we use a calculator, the calculator does not automatically account for significant figures, so we have to do so ourselves. There are some basic rules for handling significant figures in calculations as shown in the table and outlined to the right.

Significant Figure in Calculations MULTIPLICATION 123.1

Typesetting math: 100%

23 = 2800

DIVISION 123.1 / 23 = 5.4

4 s.f. 2 s.f. 2 s.f.

4 s.f. 2 s.f. 2 s.f.

ADDITION

SUBSTRACTION

123.1 + 23 = 146 1 d.p

123.1 - 23 = 100

0 d.p. 0 d.p.

1 d.p. 0 d.p. 0 d.p. note: s.f. stands for "significant figures" d.p. stands for "digits to the right of the decimal point"

Part A Compute

. Round the answer appropriately.

Express your answer numerically using the proper number of significant figures. You did not open hints for this part. ANSWER:

Part B Compute

. Round the answer appropriately.

Express your answer numerically using the proper number of significant figures. You did not open hints for this part. ANSWER:

Part C Compute

. Round the answer appropriately.

Express your answer numerically using the proper number of significant figures. You did not open hints for this part. ANSWER:

Part D Compute

. Round the answer appropriately.

Express your answer as an integer using the proper number of significant figures (e.g. 12300). You did not open hints for this part. ANSWER:

Converting Units Learning Goal: To Typesetting math: 100% ric units expressing length, area, and volume.

The ability to convert from one system of units to another is important in chemistry. It is often impractical to measure quantities in the standard meters, kilograms, and seconds, but the laws of science that you learn will involve constants that are defined in these units. Therefore, you may often have to convert your measured quantities into different metric units. The following table lists metric prefixes that come up frequently in chemistry. Learning these prefixes will help you in the various exercises.

When doing unit conversions, you need a relation between the two units. For instance, in converting from millimeters to meters, you can look at the table relating prefixes to their meanings and see that milli means

. Therefore,

Once you know this, you need to divide one side by the other to obtain a ratio of

If you are converting from millimeters to meters, then this is the proper ratio. It has converting. For instance, if you were converting , then you would have

To convert a quantity from meters to millimeters, use the reciprocal ratio:

Part A Suppose that you measure a pen to be 10.5

long. Convert this to meters.

Express your answer in meters. You did not open hints for this part. ANSWER: 10.5

=

Part B Complete previous part(s) Part C Complete previous part(s) Part D Complete previous part(s)

Substances have both chemical properties and physical properties.

Part A Which of the following properties of zinc are chemical properties? Check all that apply. You did not open hints for this part. ANSWER:

Typesetting math: 100%

to

:

in the denominator, so that it will cancel the units of the quantity that you are

It is a bluish, white-colored metal. It has a mass of 65.38 . It reacts with chlorine to form zinc chloride. It burns under a flame giving off zinc oxide fumes.

Part B Which of the following properties of a chalk are physical properties? Check all that apply. You did not open hints for this part. ANSWER: When a drop of dilute hydrochloric acid is placed on a piece of a chalk, carbon dioxide escapes. It is white in color. It is brittle. It has a mass of 1.1 .

Atomic Structure and Properties of Subatomic Particles Atoms contain three subatomic particles: protons, electrons, and neutrons.

Part A Sort each of the items into the appropriate bin. Use the diagram of a neutral lithium atom for reference. Drag each item to the appropriate bin.

You did not open hints for this part. ANSWER:

Typesetting math: 100%

Reset

particle labeled "B"

particle labeled "A"

approximately the same mass as a neutron

smallest mass of the three particles

Help

+1 charge

-1 charge

no charge

particle labeled "C"

Subatomic Particles Learning Goal: To determine the number of protons, neutrons, and electrons in a given isotope or ion. Atoms are composed of three fundamental particles. Protons are positively charged, neutrons are neutral, and electrons are negatively charged. Protons and neutrons are clustered into a dense core called the nucleus, whereas electrons are found outside of the nucleus at a relatively large distance. Elements differ from one another by how many protons their atoms they contain. The number of protons is called the atomic number ( ) of the element. Since protons and neutrons make up most of the mass of an atom, the sum of the protons and neutrons is its mass number ( ). In neutral atoms, the numbers of protons and electrons are equal. In ions, the numbers of electrons and protons are not equal.

Part A Specify the number of protons, neutrons, and electrons in the neutral atom chromium-52. Enter your answers as integers separated by commas. You did not open hints for this part. ANSWER: protons, neutrons, electrons

Part B The ion

has _____ protons and _____ electrons.

Enter your answers as integers separated by a comma. You did not open hints for this part. ANSWER:

Part C What isotope has 13 protons and 14 neutrons? Enter the name of the element followed by a hyphen and the mass number (e.g., uranium-234). You did not open hints for this part. Typesetting math: 100%

ANSWER:

Part D Which element does

represent in the following expression:

?

Enter the chemical symbol of the element. You did not open hints for this part. ANSWER:

± Neutrons and Isotopes Periodic table The periodic table lists two main numbers for each element. The atomic number is an integer that equals the number of protons. The number of neutrons is not given in the periodic table because it will vary with different isotopes. The mass number of an element is the sum of the protons and neutrons. To find the number of neutrons, the atomic number must be subtracted from the mass number. Elemental symbol When writing the symbol for an element, a superscript indicates the mass number and a subscript indicates the atomic number. For example, 14 and an atomic number of 6. This isotope can also be written as just which isotope you are dealing with.

has a mass number of

. You do not need to put in the 6 because the atomic number of carbon is always 6 regardless of

Part A How many neutrons are found in one atom of

?

Express your answer numerically. You did not open hints for this part. ANSWER:

Atomic mass Since the number of neutrons varies in the periodic table, neither then number of neutrons nor the mass number (number of neutrons plus protons) is shown. What we do see is the atomic mass, or a weighted average of all the isotope masses. This is the noninteger listed with an element; it is the number with several decimal places. An element's atomic mass is the weighted average of the isotope masses. In other words, it is an average that takes into account the percentage of each isotope. To find the weighted average, multiply each isotopic mass by its relative abundance and find the sum for each isotope of an element.

Part B A certain element

has four isotopes.

5.845% of has a mass of 53.93961 . 91.75% of has a mass of 55.93494 . 2.123% of has a mass of 56.93539 . 0.2820% of has a mass of 57.93328 . What is the average atomic mass of element ? Express your answer numerically to four significant figures. You did not open hints for this part. ANSWER:

Part C Complete previous part(s) Part D Typesetting math: 100%

The two isotopes of chlorine are

and

. Which isotope is the most abundant?

You did not open hints for this part. ANSWER:

± Counting Atoms using Avogadro's Number Matter is made up atoms, but in a real chemistry lab, we measure substances in grams. Therefore you need to be able to convert from grams to numbers of atoms, and vice versa. Quartz, which contains one silicon atom and two oxygen atoms per formula unit, is the second-most-common mineral on Earth after feldspar. It is used as a gemstone, as well as in pressure gauges, oscillators, resonators, wave stabilizers, heat-ray lamps, and prismastic lenses, and in the manufacture of glass, paints, abrasives, and precision instruments such as watches.

Part A What is the chemical formula for quartz? Express your answer as a chemical formula. You did not open hints for this part. ANSWER: formula for quartz =

Part B How many oxygen atoms are in 3.50

of quartz?

You did not open hints for this part. ANSWER: number of O atoms =

Cations and Anions An atom is made up of a positively-charged nucleus surrounded by negatively-charged electrons. The atom is neutral when there are equal numbers of protons and electrons. Ions are formed when there are unequal numbers of protons and electrons in an atom. A positive ion is called a cation whereas a negative ion is called an anion.

Part A Match each diagram to the atom or ion it represents. Drag each item to the appropriate bin. You did not open hints for this part. ANSWER:

Typesetting math: 100%

Reset

Help

Reset

Help

Part B What is the charge on the most stable ion of each of the following elements? Drag each item to the appropriate bin. You did not open hints for this part. ANSWER:

Al

O

Mg

I

S

Ba

N

K

The Periodic Table Learning Goal: To understand the arrangement of the periodic table and identify certain groups of elements by name (e.g. halogens, metals, lanthanides etc.). The periodic table is a list of elements arranged by atomic number. As you can see in the image below, the atomic number for each element is the whole number in the cell. The atomic mass, written below the symbol here although it may appear elsewhere in some periodic tables, is the average mass of the isotopes of that element. Typesetting math: 100%

Groups and periods Columns in the periodic table are called groups, and the rows are called periods. Notice that the groups are labeled 1 to 18 and the periods are labeled 1 to 7. Groups 1, 2, and 13 to 18 are called the main group elements, groups 3 to 12 are the transition elements, and the bottom two rows are called the lanthanides and actinides, respectively. This table gives properties and alternate names for some of the groups: Group

Name

Properties

1

Alkali metals

React to form 1+ ions.

2

Alkaline earths

React to form 2+ ions.

17

Halogens

React to form 1

Rare gases (noble gases)

Stable and unreactive. (Elements from other groups form ions to achieve the same number of electrons as a noble gas.)

18

ions.

Metals vs. nonmetals Notice the heavy zigzag line running diagonally across the right part of the table. This line separates metals (below and to the left of the line) from the nonmetals (above and to the right of the line). Metals tend to lose electrons to form positive ions, whereas nonmetals tend to gain electrons to form negative ions.

Part A What is the atomic number of the element located in group 16, period 2 of the periodic table? Enter the atomic number. You did not open hints for this part. ANSWER:

Part B If a new element were discovered and it was found to form 1 Enter the group number. You did not open hints for this part. ANSWER:

Part C Which of the following elements is not a metal? You did not open hints for this part. ANSWER:

iron aluminum sodium phosphorus

Part D Which of the following is not an element? You did not open hints for this part. ANSWER: Typesetting math: 100%

ions, in which group would you place it in the periodic table?

water lithium sulfur lead

Ionic versus Covalent Bonding Chemical bonds are usually classified as either covalent or ionic. A covalent bond occurs when atoms share electrons. The resulting cluster of atoms is called a molecule, and the compound is considered to be molecular. An ionic bond results from a transfer of one or more electrons from one atom to another. This creates oppositely charged ions that group together into large macroscopic lattices as opposed to small clusters. For this reason, ionic compounds are not considered to be molecular. As a general rule, covalent bonds occur between two nonmetal atoms whereas ionic bonds occur between a metal and a nonmetal atom.

Part A Which of the following would you expect to be a molecule and which would you expect to be part of an ionic solid? Drag the appropriate compounds to their respective bins. You did not open hints for this part. ANSWER:

Reset

NaI

CaS

KCl

MgO

KF

CO

SO

Part B Classify the following compounds as having covalent or ionic bonds. Drag the appropriate compounds to their respective bins. You did not open hints for this part. ANSWER:

Typesetting math: 100%

HCl

Help

Reset

sulfur trioxide

aluminum sulfide barium chloride

strontium iodide

Help

phosphorus trichloride

potassium iodide

Acid Names Acids are compounds that have at least one ion that can dissociate from the compound in solution. Precise naming of acids is important because different acids have very different properties. For example, acetic acid in dilute form is used in cooking (as vinegar), whereas hydrofluoric acid is so toxic that even splashing a small amount on the skin can be fatal without proper treatment. Naming binary acids When naming acids, start by naming the anion. A monatomic anion, such as is named chloride and is named oxide.

, is simple named by replacing the ending of the element name with ide. For example,

Once the anion is named, name the acid based on this anion. Start by adding the prefix hydro, and then change the ide suffix to ic. For example, anion chloride to be changed to chloric. Adding the prefix hydro creates hydrochloric acid.

would require the

Part A What is the name of the acid whose formula is

?

Spell out the full name of the acid. You did not open hints for this part. ANSWER:

Naming oxoacids Oxoacids contain an oxygen atom in the anion. To name them, again, start with the name of the anion when naming acids. Polyatomic anions are named according to the following rules: If an element can only form two oxyanions then the one with the least amount of oxygens is given the ending ite. The one containing the most oxygens is given the ending ate. Elements that can form four polyatomic oxyanions use prefixes in addition to the ite and ate endings. The oxyanion with the least amount of oxygens is given the prefix hypo and the ending ite (i.e., is hypochlorite). The oxyanion with the second least amo...