TEAS 7 - Science (Solutions and Chemical Reactions)

Question 1

Water is known as the universal ___.

Answer 1

solvent

Question 2

In chemistry, opposites ___.

Answer 2

attract

Question 2

Water is a universal solvent because of its unique ___, where one side has a positive charge and the other side has a negative charge.

Answer 2

polarity

Question 3

The positive ends of water will attract the ___ ends of other molecules and the negative end of water will attract ___ ends of other molecules.

Answer 3

negative

positive

Question 3

Within a water molecule, the bond between the hydrogen atom and oxygen atom is known as a ___ bond. However, the bond between the hydrogen atom of one water molecule and the oxygen atom of another water molecule is called a ___ bond.

Answer 3

covalent

hydrogen

Question 4

What allows water molecules to bind together?

Answer 4

hydrogen bonds

Question 5

What gives water its high surface tension?

Answer 5

hydrogen bonds

Question 6

___ refers to the maximum amount of a substance that can dissolve in a given amount of solvent at a specific temperature.

Answer 6

Solubility

Question 7

What is the unit for concentration?

Answer 7

molarity

Question 8

Molarity is a unit that shows how ___ a solution is.

Answer 8

concentrated

Question 9

What is the Molarity of a solution with 45 moles dissolved in 0.50 L of water?

Answer 9

M = mols/L

M = 45 mols/ 0.05L

M = 90 M

Question 9

What would be the Molarity of a solution with 100.0 moles of Kool-Aid powder dissolved in 450.0 mL of water?

Answer 9

M = mols/L

mols = 100.0
L = 450 mL = 0.450 L

M = 100 mols/ 0.450 L

M= 222 M

Question 10

Gabby has a 0.500 L of a 2.5 M solution of Copper Sulfate. She wants a 1.25 M solution. Describe how she could do this by just adding water.

Answer 10

M1V1 = M2V2

M1 = 2.5M
V1 = 0.500L
M2 = 1.25 M
V2 = ?

(2.5M)(0.500L) = (1.25M)(V2)
V2 = [(2.5M)(0.500L)] / 1.25M
V2 = 1.00L

Question 11

What is teh unit of molarity?

Answer 11

moles/Liter

Question 12

Balance the following chemical equation:

CH4 + Cl2 → CCl4 + HCl

Answer 12

CH4 + 4 Cl2 → CCl4 + 4 HCl

*CH4 + Cl2 → CCl4 + HCl
C: 1 C: 1
H: 4 H: 1
Cl: 2 Cl: 5

CH4 + Cl2 → CCl4 + 4 HCl
C: 1 C: 1
H: 4 H: 4
Cl: 2 Cl: 8

CH4 + 4 Cl2 → CCl4 + 4 HCl
C: 1 C: 1
H: 4 H: 4
Cl: 8 Cl: 8

Question 13

Which type of chemical reaction is demonstrated by the reaction below?

Ba(NO3)2 + Na2SO4 → BaSO4 + 2 NaNO3

Answer 13

Double replacement

*In a double replacement reaction, two metal ions (Ba²+ and Na+) switch places with each other in two ionic compounds

Question 13

Which of the following compounds contains ionic bonds?

Answer 13

NaBr

Question 13

In a redox reaction, oxidation is the _______ of electrons and reduction is the _______ of electrons.

Answer 13

loss; gain

Question 14

What is the “memory trick” for oxidation and reduction?

Answer 14

“OIL RIG,” which stands for “Oxidation Is Loss (of electrons)” and “Reduction Is Gain (of electrons)”

it means that when a substance loses electrons, it is oxidized, and when it gains electrons, it is reduced.

Question 14

Which of these statements is true about pH?

Answer 14

• higher pH values would have a lower [H+]
• lower pH values would have a higher [H+]
• A pH of 6 is more acidic than a pH of 8

Question 15

The same single-replacement reaction is run in two different beakers. The beakers are labeled as Beaker A and B and are heated to 75oC and 100oC, respectively. If the reactions are run for 15 minutes each, which of the following results would you expect to observe?

Answer 15

Beaker B produces more product than Beaker A

*As the temperature of a reaction increases, the reaction rate increases as well. This is due to an increased number of collisions that occur between molecules during a reaction. Since Beaker B is at a higher temperature, it should produce more product than Beaker A since the reaction times are equal.

Question 15

Balance the following chemical equation:

C3H8 + O2 → CO2 + H2O

Answer 15

C3H8 + 5 O2 → 3 CO2 + 4 H2O

*C3H8 + O2 → CO2 + H2O
C: 3 C: 1
H: 8 H: 2
O: 2 O: 3

C3H8 + O2 → 3 CO2 + H2O
C: 3 C: 3
H: 8 H: 2
O: 2 O: 7

C3H8 + O2 → 3 CO2 + 4 H2O
C: 3 C: 3
H: 8 H: 8
O: 2 O: 10

C3H8 + 5 O2 → 3 CO2 + 4 H2O
C: 3 C: 3
H: 8 H: 8
O: 10 O: 10

Question 16

Br2 is classified as which of the following?

Answer 16

Molecule

*Br2 is classified as a molecule because it is composed of two atoms of the element, Br.

Molecules are substances that are composed of two or more atoms.

Compounds are substances that are composed of two or more different types of atoms (H2O is an example since it contains both H and O).

An element is a substance whose atoms all have the same number of protons (same chemical identity), and Br2 is the elemental form of bromine.

An ion is a charged atom or molecule and will contain a (+) or (-).

Question 17

Predict the missing product of the following reaction:

Zn + 2AgNO3 → 2Ag + _________

Answer 17

Zinc nitrate

*The reaction above is an example of a single replacement reaction, where one metal ion replaces another in an ionic compound. The starting compounds are zinc (Zn) and silver nitrate (AgNO3). Zn replaces Ag in AgNO3 to form Zn(NO3)2. Although similar, zinc nitrite has the formula Zn(NO2)2.

Question 18

Correctly identify X in the reaction below:

210⁄84 Po → X + 4⁄2 He

Answer 18

206/82 Pb

*The type of radioactive decay shown in the reaction above is alpha decay where a nucleus emits an alpha particle (a Helium nucleus). The alpha particle is composed of 2 neutrons and 2 protons. The numerator in front of the Po indicates the mass number of the isotope, which is the sum of the protons and neutrons of the atom. The denominator represents the atomic number, which is the number of protons. To obtain the identity of the missing isotope X, just subtract the mass number and number of protons from the original atom.

Since the number of protons is 82, the identity of the atom is lead (Pb) since Pb has an atomic number of 82.

Question 18

How many moles of O2 will be produced when the reaction below is properly balanced?

H2O2 → H2O + O2

Answer 18

1 mole

*The properly balanced equation above will be 2 H2O2 → 2 H2O + O2. In chemical reactions, the coefficients (numbers in front of reactants and products) equal the number of moles of that chemical species. Since there is no number in front of O2, a coefficient of 1 is implied, which means there is 1 mole of O2 produced in this reaction.

Question 19

Which of the following is an example of a redox reaction?

Answer 19

Combustion

*A redox reaction is one that involves the transfer of electrons between two species. The substance that gives away electrons is said to be oxidized. The substance that receives the electrons is said to be reduced. During combustion, elemental oxygen (O2) reacts with a compound to form products that contain oxygen. This requires oxygen to transition from a neutral oxidation state (0) to an oxidation state of -2. (The oxygen has been reduced.)

In the other reaction choices, the oxidation states of atoms do not necessarily change.

Question 19

Identify the acid in the following reaction:

CH3COOH + NaOH → NaOOCCH3 + H2O

Answer 19

CH3COOH

*The acid in a reaction is the species that donates a hydrogen (H) to the base (NaOH in this reaction). In the reaction above, CH3COOH donates a H to NaOH to form NaOOCCH3 and H2O. The name of this acid is acetic acid, which is also called vinegar.

Question 19

Which of the following are produced from the reaction between a Brønsted-Lowry acid-base pair?

Answer 19

A salt and water

*A Brønsted-Lowry acid donates a proton (H+) during a reaction. When the protonated species is a base, the hydroxyl (-OH) from the base combines with the H+ of the acid to form water. The counterions of the acid and base combine to form a salt.

Question 20

Which of the following scenarios will increase the likelihood of reactant molecules colliding with one another during a liquid chemical reaction?

Answer 20

Increasing the reaction concentration

*The rate of a reaction depends on the frequency at which reactant molecules collide with one another. By increasing the concentration of reactants, there are more molecules of reactants in a given space, which increases the likelihood that these molecules will collide with one another.

The question specifies that the reaction is liquid, which means that increasing the pressure will have no effect on the reaction rate, since this only affects gaseous reactions.