Latest Physical Science Reviewer 13 - LET EXAM - Questions & Answers

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Latest Physical Science Reviewer 13



1. A week attraction between hydrogen atom in one molecule and an oxygen in other called_______.
A. covalent bond
B. Hydrogen bond
C. Ionic bond
D. Metallic bond

Ans: B. Hydrogen bond
-   Hydrogen bond only form between hydrogen and oxygen, nitrogen or fluorine. Hydrogen bonds are very specific and lean to certain molecules having special properties due to these types of bonds.

2. Which of the following substances  is most likely a covalent compound ?
A. CaCO3
B. KNO3
C. SO2
D. NaOH

Ans: C. SO2
-Sulfur and oxygen are both non-metals which what form covalent bond.

3. What is the element needed to bond with Na to create the most ionic bond?
A. F
B. C1
C. Br
D. I

Ans: A. F
-When two atoms combine, the nature of the bond between them is determine by the difference in their electronegativity. The choices belong to Group VII-A. The arrangement of these elements in the periodic table indicate that F (fluorine) being on top has the highest electronegativity. Therefore, it can create the most ionic bond.

4. The boiling point of substance A is higher than that of substance B. What does this meaning?
A. Substance A is less viscous than substance B.
B. Substance A evaporates faster than substance B.
C. Substance B has greater surface tension than substance A.
D. Substance B has weaker intermolecular forces than substance A.

Ans: D. Substance B has weaker intermolecular forces than substance A.
-The boiling point of a compound is the temperature at which a compound turns from a liquid to a gas or a gas to a liquid. This temperature is a measure of the forces of attraction that exist between molecules in a compound. The higher the intermolecular forces, the higher the boiling point.

5. What is the intermolecular force of attraction between the nucleus of one atom and the electrons of a nearby atom?
A. Dipole-dipole force
B. Ion-dipole force
C. London dispersion force
D. Van der Waals force


Ans: C. London dispersion force
-All atoms and molecules combine have a weak attraction for the one another known as van der Waals attraction. This attractive force has its origin in the electrostatic attraction of the electrons of one molecule or atom for the nuclei of another, and has been called London dispersion force.

6. Which of the following has the greatest number of atom?
A. Ca(OH)2
B. A12O3
C. NaHCO3
D. C2H2

Ans: C. NaHCO3
-Ca(OH)2 has 5 atoms, A12O3 HAS 5 ATOMS, NaHCO3 has 6 atoms and C2H2 has 4 atoms.

7. What does a triangle , which is placed in a chemical equation indicate?
A. Changes happened
B. Heat is applied
C. Gas is evolved
D. Precipitate
Ans: B. Heat is applied
- May mean changes happened but not in a chemical equation. Triangle in a chemical equation indicates that is applied to make the reaction proceed. Arrow down Is the symbol for evolution of gas. Arrow down Is the symbol to indicate precipitate is formed.

8. What would most probably be the resulting chemical formula when Mg+2and O-2combine?
A. MgO
B. Mg2O2
C. MgO­2
D. Mg4O4
Ans: A. MgO
-Using criss-cross method combining Mg2+result tot Mg2O2 but it needs to be reduced to lower whole number ratio which is MgO.

9. Which of the following is an example of combustion reaction?
A. Mg+C12  -------------------------------------> MgC12
B. CaCO3     -------------------------------------> CaO + CO2
C. 2 C4H10 + 13 O2  ----------------------------------> 8 CO2 + 10 H2­­O
D. AgNO3 + NaC1 --------------------------------> AgC1 + NaNO3
Ans: C. 2 C4H10 + 13 O2 ---------------------------------->  8 CO2 + 10 H2­­O

-A combustion reaction usually occurs when a hydrocarbon react with oxygen to produce carbon dioxide and water. It is an exothermic reaction so it releases heat.


10. What type of chemical reaction is involved in Ca­(S) + 2H2O Ca(OH)2(aq)?
A. Combination
B. Decomposition
C. Single-displacement
D. Double-displacement

Ans: C. Single-displacement
-Single displacement happens when one element trades places with one another element in a compound. In the item, hydrogen is replaced in water   by calcium forming a new compound plus hydrogen gas. Combination reaction occurs when two or more simple compounds combine to form a more complicated one. Decomposition happens when a complex molecule breaks down to make simpler ones. Double displacement occurs when the anions and cations of two different molecules switch places, forming two entirely different compounds.

11. When the fuel in a butane gas stove undergoes complete combustion, it reacts with oxygen to form carbon dioxide and water:_C4H10 +  _ O2CO­2+_H2O. Which set of coefficients can be BEST used in balancing the equation?
A. 1, 1, 4, 2
B. 2, 2, 4, 5
C. 2, 8, 13, 10
D. 2, 13, 8, 10
Ans: D. 2, 13, 8, 10
-     Reactions                                                          Product
C=  2 x 4 = 8                                              C=  8 x 1 = 8
H= 2 x 10 = 20                                           H= 10 x 2 = 20
O= 13 x 2 = 26                                           O= 8 x 2 =16
                                                                  O= 10 x 1 = 10

12. In oxidation-reduction, the oxidizing agents is reduced and gains electrons. The reducing agent is oxidized and loses electrons. Are the statements CORRECT?
A. Both statements are correct.
B. Both statements are false
C. First statement is true; second statement is false.
D. Second statement is true; first statement is false.

Ans: A. Both statements are correct.
- Oxidation-reduction (redox) involves a transfer of electrons between two species. It is comprised of two parts, a reduced half and an oxidized half, that always occurs together. The reduced half gains electrons and the oxidation number decrease, while the oxidized half losses electrons and the oxidation number increases. Simple way to remember this is the mnemonic device OIL RIG meaning Oxidation Is Low Reduction is Gain.

13. How many moles of iron does 25 g of Fe represent? (Fe=55.85 g)
A. 0.448 mol
B. 2.234 mol
C. 30.85 mol
D. 80.85 mol
Ans: A. 0.448 mol
-          (25 g) / ( 55.85 g/mol ) =0.448 mol

14. What is the mass of 5.0 mol of water? (1 mol H2O=18.02g)
A. 3.60 g
B. 13.02 g
C.23.02 g
D. 90.10 g
Ans: C. 90.10 g
-(5 mol) (18.02 g/mol ) = 90.10 g

15. An analysis of salt shows that it contains 56.58 g potassium; 8.68 g carbon and 34.73 oxygen. What is the empirical formula of the substance?
A. KC2O3
B. K2CO­2
C. K2CO3
D. K2C3O
Ans: C. K2CO3
-K (56.58 g) / ( 39.10 mol/g ) = 1.447 mol             Divide the result by the     2
 C (8.68 g ) / ( 12.01 mol/g ) = .723 mol                lowest answer which         1
 O (34.73 g) / (16 mol/g) = 2.171mol                     is .723                             3

16. Which of the following is NOT a principal assumption of Kinetic Molecular Theory?
A. Gas particles move rapidly.
B. Gases consists of submicroscopic particles.
C. There is very little empty space in a gas.
D. Gas particles have no attraction for one another.

Ans: C. There is very little empty space in a gas.
-Options A, B, and D are true. Gas particles are much smaller than the distance between the particles. Most of the volume of a gas is therefore empty space.

17. Based on the Kinetic Molecular Theory, a gas can be compressed much more than a solid or liquid because__________.
A. gas particles move rapidly
B. the particles of a gas are very far apart
C. a gas is composed do not attract or repel one another
D. gas particles do not attract or repel one another

Ans: B. the particles of a gas are very far apart
-Sold are difficult to compress as the particles are already paced closely together. Liquids are difficult to compress because there are quite a lot of particles in small volume. Gases are easily compressed because there are only few particles in a large volume.

18. Which refers to the kinetic energy or motion of gas particles?
A. Pressure
B. Quantity of gas
C. Temperature
D. Volume

Ans: C. Temperature
-An input of heat can cause an increase in temperature because the input of heat is realized as an increase in the kinetic energies of the gas molecules. When the average kinetic energy of the gas molecules goes up, the temperature goes up.

19. A given mass of gas has a volume of 750 ml at -25 and 280 torr. What would the volume of the gas be at 30 and 560 torr of pressure considering the amount of gas which is constant?
A. 450  ml
B. 458 ml
C. 480 ml
D. 520 ml
Ans: B. 458 ml
This item involves combined gas law : P1V1 = P2V2
                                                        T1             T2

20. Seven liters of an ideal gas are contained at 3.5 atm and 30How many moles of this gas are present?
A. 0.50 mol
B. 0.75 mol
C. 1.00 mol
D. 1. 25 mol

Ans: C. 1.00 mol
-  n=PV/RT
n= (3.5 atm x 7 L ) / (.08 L atm/mol K x 303 K) = 1.00 mol

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