Latest Physical Science Reviewer 14

1. An odorless and colorless matter boils at 100 ℃ and melts at 0 ℃ What inference can be drawn from this observation?

A. It is a metal.

B. It is a mixture

C. It is a non-metal.

D. It is a pure substance.

Ans: D. It is a pure substance.

-A pure substance is a sample of matter with both definite and constant composition. Pure substances melt or boil are particularly sharp, meaning melting or boiling occurs at a single temperature.

2. You want to clean a tarnished silver. Which one will you use?

A. Baking soda

B. Salt solution

C. Sugar solution

D. Vinegar

Ans: A. Baking soda

Baking soda (sodium bicarbonate) helps living things maintain the Ph balance necessary for life. It acts as a cleaning agent because it is mild alkali and can cause dirt and grease to dissolve easily in water.

3. What will you add to your food to make it last longer?

A. Baking soda

B. Salt solution

C. Tomato

D. Vinegar

Ans: D. Vinegar

Vinegar is acidic so it would significantly retard the growth of bacteria that cause food spoilage.

4. Why is it not advisable to drink soft drinks on an empty stomach?

A. It could lessen your appetite.

B. It could make you feel full faster.

C. It increases the acidity of your stomach.

D. It contains stimulant which causes dizziness.

Ans: C. It increases the acidity of your stomach.

- If you are hungry, then the only thing in your stomach is acid. Soft drinks are acidic and drinking it while you’re hungry makes the stomach more acidic.

5. Almost the entire mass of an atom is concentrated in the __________?

A. electron

B. neutron

C. nucleus

D. proton

Ans: C. nucleus

-Nucleus is the central part of an atom that contains proton and neutron that’s why almost the entire mass of the atom is concentrated on it.

6. How many protons are present if an atom has  a mass number of 23 and atomic number of 11?

A. 11

B. 12

C. 23

D. 44

Ans : A. 11

-Atomic number is the number of protons found in the nucleus of an atom. The atomic number is 11 so the number of protons is also 11.

7. Carbon-12 atom has ______________.

A. 6 electrons, 6 protons, 6 neutrons

B. 6 electrons, 12 protons, 6 neutrons

C. 12 electrons, 6 protons, 6 neutrons

D.  16 electrons, 6 protons , 6 neutrons

Ans: A. 6 electrons, 6 protons, 6 neutrons

- The number 12 in carbon-12 is the atomic weight. This is the total number protons and neutrons. The atomic number of carbon is 6, it follows that the number of protons is also 6. The number of neutrons is 6 so that if added to protons, the result is 12 which is the atomic weight

8. What happens to the atomic number during a chemical reaction?

A. Changes

B. Remains the same

C. Changes the alternately

D. Changes and then is restored

Ans: B. Remains the same

-In chemical reactions, the most important property to be conserved is the number of atoms of each kind that present. Chemical reaction do not create nor destroy atoms, nor change one kind of atom into another. They only reshuffle the atoms that were originally present into different molecular neutrons combinations. Hence, atomic number remains the same.

9. Which of the following statements about isotopes of hydrogen is correct?

A. They have different atomic numbers.

C. They have the same number of neutrons .

B. They have the same number of protons.

D. They have different number of electrons.

Ans: B. They have the same number of protons.

-Isotopes are atoms of elements with different number of neutrons. The most common isotope of hydrogen has no neutrons at all; a hydrogen isotope called deuterium has one neutron; another hydrogen isotope known as tritium has two neutrons. All isotopes of hydrogen have the same number of protons.

10. Which of the following has 16 electrons?

A. ²⁷₁₃A1⁺³

B. ³⁵₁₇C1^-1

C. _­³²₁₆S

D. ³²₁₆S^-2

Ans: C. _­³²₁₆S

-A convenient way of writing the numbers that describes atom is by writing atomic number below and the mass number above, followed by its symbol along with the charge. The charge is the difference in the number of protons compared to the number of electrons. The number of electrons is equal to the number protons is in neutral state.

11. How many protons, neutrons and electrons are there in an atom of ¹⁹⁷₇₉Au?

A. 79 protons, 79 electrons, and 118 neutrons

B. 79 protons, 79 electrons, and 197 neutrons

C. 197 protons, 79 electrons, and 79 neutrons

D. 79 protons, 79 electrons, and 158 neutrons

Ans: A. 79 protons, 79 electrons, and 118 neutrons

-79 is whiten below so it is the atomic number which is equivalent to number of protons and electrons. 197 is the atomic weight. 197-79 =neutrons.

12. The electrons configuration of an atom of element R in the ground state is 1s²2s²2p⁶3s²3p⁶4d⁹. What is the element described?

A.₄₈Cd

B. ₃₅Br

C. ₃₁Ga

D. ₂₇Co

Ans: C. ₂₇CO

- Adding all the superscripts 2+2+6+2+6+9 will result to 27 which indicates the number of electrons in the atom.

13. What is the shape of the molecule BeC1₂?

A. Linear

B. Angular

C. Trigonal planar

D. Tetrahedral

Ans: A. Linear

- The molecular geometry of BeC1₂ is linear triatomic. There are two bonding pairs and the non-bonding pairs on the central Be atom. The bond angle is degrees.

14. The generalized electron configuration of this group of element is [Noble gas] ns²ns. Identify its group and family.

A. Group VII and Family A

B. Group V and Family A

C. Group III and Family B

D. Group I and   Family B

Ans: A. Group VII and Family A

-The ending configuration is ns²np⁵. It indicates that the electrons are on the same group, so 2+5=7. The element belongs to Group VIIand since the ending is on the p-block, the element belong to family A.

15. What is the position of ₁₂Mg in the periodic table of elements?

A. Group I-A, Period 2

B. Group III-A, Period 2

C. Group II-A, Period 3

D. Group II-B, Period 4

Ans: C. Group II-A, Period 3

- The electron configuration of ₁₂Mg is 1s²2s²2p⁶3s². The ending configuration is 3s², so Mg belongs to Group II-A as indicated by s² and Period 3 as suggested by the number 3 in 3s².

16. What happens when a metal react with a nonmetal ? Usually___________.

A. a simple covalent bond is formed

B. a coordinate covalent bond is formed

C. positive and negative ions are formed

D. there is sharing of electrons in the outer shells of two elements

Ans: C. positive and negative ions are formed

-Ionic bonds form between metals and non-metals. Metals tend to lose electrons and non-metals tend to gain electrons, so in reactions involving these two groups, there is electron transfer from the metal to the non-metal that forms positive and negative ions.

17. What bond exists in a solid that does not conduct electricity but conducts electricity when dissolved in water?

A. Coordinate covalent bond

B. Covalent bond

C. Ionic bond

D. Metallic bond

Ans: C. Ionic bond

-In order for a substance to conduct electricity, it must have charged particles that can move freely. In solid ionic compounds, charged ions are locked in place, held tightly together in crystal lattice and cannot move freely. As aqueous or gas, ionic compounds, do not conduct electricity because ions have dissociated and are free to move.

18 .Which of the following statements about a triple bond is CORRECT?

A. Compounds with triple bonds are not reactive.

B. An example of a molecule with a triple bond is C₂H₆.

C. Triple bond is weaker than single and double bonds.

D. Three pairs of electrons can hold two atoms together stronger than two pairs.

Ans: D. Three pairs of electrons can hold two atoms together stronger than two pairs.

-A triple bond is chemical bonding between two atoms involving six bonding electrons instead of two in a covalent single bond. It is stronger and shorter compared to single bond and double bond. C₂H₆ is a molecule with a single bond only.

19. Which chemical bond will most likely exists if element A has an electron configuration of 1s²2s²2p³ and element B has 1s²2s²2p^5??

A. Coordinate covalent

B. Ionic

C. Metallic

D. Polar covalent

Ans:  D. Polar covalent bond

-Polar covalent bonds fall between ionic and covalent bonds. They result when two elements bond with a moderate difference in electronegativity but does not surpass 1.7 electronegativity difference. The element with 7 electrons is nitrogen and the element with 9 electrons is fluorine. Since they are placed near each other in the periodic table, it means that there is a moderate difference in their electronegativity. Nitrogen has an electronegativity of 3.04 and fluorine has 3.98, 3.98-3.04=.04 which is not greater than 1.7.

20. X, Y, and Z represent elements of atomic numbers 9, 11, and 16. What type of bond will be performed between Y and Z?

A. Ionic bond

B. Metallic bond

C. Nonpolar covalent bond

D. Polar covalent bond

Ans: A. Ionic bond

-In an ionic bond, a positively charged ion is attracted to a negatively charged ion. Like charges repel, so an ionic bond cannot contain two positively charged ions. Sodium has an atomic number of 11 and charge of +1. Sulfur has an atomic number of 16 and a charge of -2. The two element combine through ionic bonding forming Na₂S.

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