Chem Midterm Exam Practice Exam

The smallest unit of matter that retains the properties of that matter is

an atom

Which of the following is an extensive property of matter?:

- boiling point

- density

- volume

- melting point

boiling point

Which of the following is an intensive property of matter?:

- energy content

- density

- volume

- mass

density

Which of the following is a physical change of matter?:

- water evaporating

- paper burning

- a nail rusting

- a silver spoon tarnishing

water evaporating

Which state of matter is composed of atoms that have lost many of their electrons?

plasma

Which of the following changes is a chemical change of matter?:

- ice melting to produce water

- vinegar combining with baking soda to produce carbon dioxide

- water boiling to produce water vapor

- liquid silica solidifying to form glass

vinegar combining with baking soda to produce carbon dioxide

In general, which properties are common to elements within a single group on the periodic table?

chemical properties and ability to bond to other atoms

Which of these recorded observations is qualitative, rather than quantitative?:

- a chemical reaction is complete in 2.3 s.

- The solid has a mass of 23.4 g

- The compound melts at 87.5 C

- Iron is denser than aluminum

Iron is denser than aluminum

The unit cm^3 is used to express

volume

The SI base units for time and temperature are

second and kelvin

The conversion factor 1L/10^3mL would be used to change

milliliters to liters

A sample of bismuth has a mass of 343 g and a volume of 35.0 cm^3. What is the density of bismuth? And how do you calculate the density?

9.80 g/cm^3

- you divide the mass by the volume

d=m/v

Which of these statements about density is true?:

- Density is proportional to the amount of a substance

- Density is expressed in units of mL/cm^3

- Density does not change with temperature

- Density may be used to help identify a material

Density may be used to help identify a material

The SI base unit for mass is the

kilogram

Precision is related to all of these except?:

- reproducibility

- range of measurement values

- number of significant figures

- closeness of a measurement to the accepted value

closeness of a measurement to the accepted value

A student determined the density of aluminum by averaging the results of three density calculations. Each value was different, but the average was equal to the accepted value for aluminum's density. The results of this investigation are best described as?

accurate, but not precise

The measurement 0.0265 g, rounded off to two significant figures, would be

0.03 g

In division and multiplication, the answer should have the same number of significant figures as the

number in the calculation with the fewest significant figures

The number of significant figures in the measurement 170.040 km is?

six

The dimensions of rectangular solid are measured to be 1.27 cm, 1.3 cm, and 2.5 cm. The volume should be recorded as? And how should you calculate this?

4.1 cm^3

- you calculate this by multiplying them all together

Samples with masses of 0.12 g, 1.8 g, and 0.562 g are mixed together. The combined mass of the three samples, expressed to the correct number of significant figures, should be recorded as?

2.5 g

Expressed in scientific notation, 0.0930 m is

9.30 x 10^-2 m

When 6.02 x 10^23 is multiplied by 9.1 x 10^-31, the product is?

5.5 x 10^-7

Which of these is an example of an extensive property?:

- mass

- density

- color

- boiling point

mass

Which process is a chemical change?:

- heating to boiling

- dissolving in alcohol

- burning in air

- slicing into two pieces

burning in air

At sea level, water boils at 100C. This is an example of a(n)?

physical property

By making several measurements of a sample with the same balance, a chemist obtained values of 5.224 g, 5.235 g, and 5.259 g for the mass of a sample. Without knowing the actual mass of the sample, we can tell that these measurements have?

low precision

The average distance between the sun and the Earth is about 150 million km. Light travels at a speed of 3.0 x 10^8 m/s. Dividing the density by the speed and then multiplying by the number of meters in a kilometer will result in units of?

seconds

If some measurements agree closely with each other but differ widely from the actual value, these measurements are

precise but not accurate

In which of the following measurements are all the zeros considered to be nonsignificant figures?

- 506 mL

- 60.0 mL

- 0.0037 mL

- 400. mL

0.0037 mL

In division and multiplication, the answer must have the same number of significant figures as the

number in the calculation with the fewest significant figures

Neutral atoms contain equal numbers of

protons and electrons

The atomic symbol for beryllium, (image), indicates that the

atomic number is 4

An atom of potassium has 19 protons and 20 neutrons. It's mass number is? And how do you do this?

39

- add the number of protons and neutrons

Which of the following is NOT equal to 1.00 mol of carbon-12?:

- 6.022 x 10^23 carbon atoms

- 12.0 g of carbon

- 6.0 g of carbon

- Both (b) and (c)

Both (b) and (c)

Compared with a mole of lead atoms, a mole of iron atoms ...

has the same number of atoms

To calculate the number of atoms present in 2.0 mol of an element, you would?

multiply Avogadro's number of atoms per mole by 2.0 mole

To determine the mass in grams of an atom of any element, you would?

divide the mass of a mole of the element by Avogadro's number

The average atomic mass of an element is

the weighted average of all naturally occurring isotopes of the element

The molecular mass of CO2 is 44.01 amu. What is the mass of 2.0 mol of CO2? And how do you calculate this?

88.02 g

- you multiply 44.01 x 2.0 together

How many moles of sodium hydroxide, NaOH, are in 35.65 g sample of NaOH? (The molar mass of NaOH is 40.01 g/mol.)

0.8910 mol

What is the mass of 3.56 mol of glucose, C6H12O6? (The molar mass of C6H12O6 is 180.18 g/mol.) How do you get this?

641 g

- You multiply 180.18 times 3.56 mol of glucose

Neutral atoms of the same element can differ in?

mass number

Most of the volume of an atom is occupied by the?

electrons

The diagram represents two electrons with?

opposite spin states

Which of the following quantum numbers describes a p-orbital in the third energy level?:

- n = 3, l = 0, m = 0

- n = 3, l = 1, m = 0

- n = 3, l = -1, m = 0

- n =4, l = 1, m = 0

n = 3

l = 1

m = 0

A proton is emitted from a gaseous atom when an electron moves to its ground state from a(n)?

excited state

Which are sublevels in an energy level of n = 3?

- s, p, and f

- s, d, and f

- s, p, and d

- p, d, and f

s, p, and d

What is the highest occupied energy level in an atom of strontium in its ground state?

n = 5

What is the correct electron configuration for a ground-state atom with 7 electrons?

- 1s^2 2s^2 2p^3

- 1s^2 2s^2 2p^2 3s^1

- 1s^2 2s^3 2p^2

- 1s^2 2s^5

1s^2 2s^2 2p^3

What is the correct noble-gas notation for the electron configuration of an atom of chlorine?

- [Ar] 3s^2 3p^5

- [Ne] 3s^2 3p^4

- [Ar] 3s^2 3p^4

- [Ne] 3s^2 3p^5

[Ne] 3s^2 3p^5

What is the atomic number of the element with the noble-gas notation [Kr] 5s^1? How do you do this?

37

- [Kr] = 36

36 + 1 =37

The electron configuration below represents a ground-state atom of which element?

sulfur

When an atom in an excited state emits a photon of radiation, the energy of the photon is equal to the?

difference in energy between the atom's excited state and its final state

How many possible orientations does an s orbital have?

1

The principal quantum number of an electron is 4. What are the possible orbital quantum numbers?

0, 1, 2, 3

What is the total number of electrons still needed to fill the fourth main energy level? (show work)

32

4s^2 4p^6 4d^10 4f^14

2+6+10+14

An orbital that would never exist in the quantum description of an atom is?

3f

Whenever an excited hydrogen atom returns from an excited state to its ground state, it

emits a proton of radiation

Which of the following requires that each of the p orbitals at a particular level have one electron before any of them can have two electrons?:

- Hund's rule

- the Pauli exclusion principle

- the Aufbau principle

- the quantum rule

Hund's rule

A chemical reaction was carried out three times. The mass of the product was 8.93 g for the first trial, 8.94 g for the second trial, and 8.92 g for the third trial. Under the conditions of the experiment, the reaction is known to yield 8.60 g of product. The three mass values measured are?

accurate

The number of significant figures in the measurement 0.000305 kg is?

three

Written in scientific notation, the measurement 0.000065 cm is?

6.5 x 10^-5 cm

What is the sum of 100.0 g and 0.01 g, expressed in scientific notation and written with the correct number of significant figures?

1.000 x 10^2 g

This is the conversion of 165 km per hour to nanometers per microsecond in scientific notation with correct number of significant figures

4.5800 x 10^4 nm/µs

The density of Au is 19 g/cm3. When melted the nugget fills 13 mL in a cylinder. This is the mass of the Gold present in kg.

2.5 x 10^-1 kg of Au

The charge on an ion is

either positive or negative

According to the octet rule, a calcium atom has a tendency to

lose two electrons

If a compound forms by ionic bonding, which is NOT true?:

- A positively charged atom or group of atoms attracts a negatively charged atom or group of atoms

- The net charge of the compound is zero

- The compound contains just two atoms, each of opposite charge

- Several ions group together in a tightly packed structure

The compound contains just two atoms, each of opposite charge

The only property listed that is NOT characteristic of ionic compounds is?:

- high melting point

- hardness

- lack of crystal structure

- brittleness

lack of crystal structure

A covalent bond is formed when two atoms?

share one or more pairs of electrons with each other

Two atoms will likely form a polar covalent bond if the electronegativity difference is?

1.0

In which of these compounds is the bond between the atoms NOT a nonpolar covalent bond?:

- Cl2

- H2

- HCl

- O2

HCl

Bonding in molecules or ions that cannot be represented by adequately by a single Lewis structure is represented by?

resonance structures

As the electronegativity difference between bonded atoms decreases, the bond becomes more?

covalent

As atoms bond with each other, they?

decrease their potential energy, thus creating more stable arrangements of matter

Which type of bonding is characterized by overlapping orbitals that allow outer electrons of atoms to move about freely throughout the entire lattice?

metallic

According to VSEPR theory, what is the shape of a molecule of NBr3?

trigonal-pyramidal

The molar mass of an element is numerically equal to?

the element's average atomic mass

The least massive particle in an atom is the?

electron

An atom consisting of protons, neutrons, and electrons is shown. State the number of protons, neutrons, and electrons that make up the pictured atom.

Protons: 7

Neutrons: 7

Electrons: 7

Use the periodic table to answer the question. Which one of the following elements has the same number of electrons in the outer shell and similar chemical characteristics as the atom shown?

As

Susan has access to the modern periodic table. She has been given samples of four elements to identify. The electron configuration of these four elements are also given to her. She observes the samples and starts to perform same simple tests to help her start identifying the samples. Her notes and observations are in the table:

Sample A: observations - narrow ribbons of a silvery, hard white solid; Electron configuration - [Ne] 3s^2

Sample B: observations - small pieces of silver-gray solid, soft and can be cut with a scalpel, stored in kerosene; Electron configuration - [Ne] 3s^1

Sample c: observations - dark brown liquid that gives off red vapors when left open and has a strong smell; Electron configuration - [Ar] 3d^10 4s^2 4p^5

Sample D: observations - dark gray, hard solid that can mark paper [He] 2s^2 2p^2

actual question on next slide

Sample A: observations - narrow ribbons of a silvery, hard white solid; Electron configuration - [Ne] 3s^2

Sample B: observations - small pieces of silver-gray solid, soft and can be cut with a scalpel, stored in kerosene; Electron configuration - [Ne] 3s^1

Sample c: observations - dark brown liquid that gives off red vapors when left open and has a strong smell; Electron configuration - [Ar] 3d^10 4s^2 4p^5

Sample D: observations - dark gray, hard solid that can mark paper [He] 2s^2 2p^2

Susan finds that sample A and B are shiny and can be hammered. Sample A is hard. Sample C and D are dull. Sample C is a liquid and sample D is brittle. Choose the correct option from the following:

- Samples A, B, C, and D are all metals

- Samples A, B, D, and D are all nonmetals

- Samples A and B are nonmetals and samples C and D are metals

- Samples A and B are metals, and samples C and D are nonmetals

Samples A and B are metals, and samples C and D are nonmetals

Susan wants to arrange the elements according to the periods in which they are found in the periodic table. How could Susan arrange the elements? Why?

Susan could use electron configuration to arrange the elements by groups

Chlorine, Z = 17, combines with sodium to form sodium chloride.

The fuming, brown liquid shows sample C (observations - dark brown liquid that gives off red vapors when left open and has a strong smell; Electron configuration - [Ar] 3d^10 4s^2 4p^5) has similar chemical properties to chlorine. Sample C forms a compound with sodium.

Based on this information, to which group does Sample C belong? What is the general name given to the group to which chlorine and Sample C belong?

- Sample C belongs to group 7A or 17

- This group is known as the halogens

Which of the following "correctly" identifies sample D (observations - dark gray, hard solid that can mark paper [He] 2s^2 2p^2) based on the number of protons, neutrons, and electrons present in an atom of sample B (Sample B: observations - small pieces of silver-gray solid, soft and can be cut with a scalpel, stored in kerosene; Electron configuration - [Ne] 3s^1)?

Sample D is a carbon because there are six protons, six electrons, and six neutrons making its atomic number 6 and mass number is 12

The diagram depicts a model of an atom. No individual subatomic particles are shown. Only the electron shells, or energy levels, and the nucleus are shown.

Look at the model. The model shows three electron shells of an atom, without any electrons.

If the valence shell has six electrons, what is the atomic number of this atom?

16

in the model shown (model of an atom), the atom has eight valence electrons. Choose the name of the element the diagram represents and the group to which the element belongs

The element is argon and it belongs to the noble gas group

A lab technician has both a sample of sodium and potassium.

She uses the periodic table to compare the properties of the two elements.

Compare the ions that the two elements form

- The Sodium and Potassium ions have noble gas electron configuration

- Both Sodium and Potassium atoms lose one valence electron and form cations with a +1 charge

- The ions have a noble gas configurations

Molecules of carbon dioxide and water have covalent bonds in their structures. In the molecules, an atom or atoms have unused pairs of electrons. From the following, select the one that applies for both carbon dioxide and water molecules.

- Both carbon dioxide and water molecules have double bonds in their structures and each of the oxygen atoms have two pairs of unshared electrons

- Both carbon dioxide and water molecules have single bonds in their structures, and each of the oxygen atoms have two pairs of unshared electrons

- A carbon dioxide molecule has two single bonds and two pairs of unshared electrons. A water molecule has one double bonds and two unused electrons.

- A carbon dioxide molecule has two double bonds and four pairs of unshared electrons. A molecule of water has two single bonds and has two pairs of unshared electrons

- A carbon dioxide molecule has two double bonds and four pairs of unshared electrons

- A molecule of water has two single bonds and has two pairs of unshared electrons

Choose the answer with the words in the correct order to complete the paragraph:

_____ is the ability of an atom of an element in a compound to attract the shared electrons toward itself. We can predict the nature of the bond between atoms of elements by finding the electronegativity difference between the atoms involved.

______ bonds show an electronegativity difference greater than 2.0 between the bonded atoms. Apart from this, there are weak forces of attraction between molecules formed by sharing electrons.

______ forces are the weakest of the forces between atoms, caused by the momentary, uneven shifting of the electron cloud among the atoms.

1.) Electronegativity

2.) Ionic

3.) Dispersion forces

Use the electronegativities of the three elements to explain how the chemical structures of water and oil allow the oil to pool on the surface of the water

Hydrogen 2.20

Oxygen 3.44

Carbon 2.55

The nonpolar oil and the polar water will not mix because the polar water molecules stick to themselves

Carbon forms many compounds with other elements. For example, carbon combines with chlorine to make carbon tetrachloride, as shown.

Carbon tetrachloride was used in the dry cleaning and pesticide industries until it was discovered that it contributed to the breakdown of the ozone layer.

Now, its use is limited.

Consider how many chlorine atoms combine with carbon. How many atoms of sulfur will combine with an atom of carbon?

two

In addition to carbon, chlorine combines with other elements to form compounds such as NaCl, CaCl2, and AlCl3. Use the periodic table to predict the charge of the barium ion when it reacts with chlorine.

+2

(look at the charge on chlorine)