Latest Physical Science Reviewer 12

1. What is the BEST reason why the atmospheric pressure in Baguio City is lower than the atmospheric pressure at sea level?

A. Because there are more gas particles at higher altitudes

B. Because there are less gas particles at higher altitudes

C. Because there are greater temperature at higher altitudes

D. Because there is lesser temperature at higher altitudes

Ans: B. Because there are less gas particles at higher altitudes

-Since gas is compressible, the density of air just like pressure decrease as the altitude increase because there is less weight above squashing it down. The higher the altitude, the lesser the gas particles, that is why it is easier to breath at ground level than at the mountain.

2. Which of the following correctly describes the process of exhalation (air going out of the lungs)?

A. The lungs decrease in volume, causing the internal pressure to increase.

B. The lungs decrease in volume, causing the internal pressure to decrease.

C. The lungs increase in volume, causing the internal pressure to increase.

D. The lungs increase in volume, causing the internal pressure to decrease.

Ans: A. The lungs decrease in volume, causing the internal pressure to increase.

-When you inhale, the diaphragm and the muscles between your ribs contract and expand the chest cavity. This expansion lowers the pressure in the chest cavity below the outside air pressure. When you exhale, the volume decreases, thereby increasing the pressure in the chest cavity above the outside air pressure.

3. What is the closed, continuous path through which electrons can flow?

A. Charge

B. Circuit

C. Resistor

D. Voltage

Ans: B. Circuit

-A circuit is composed of electronic components connected by conductive wires through which electric current flow. A charge is a property of matter that causes it to experience a force

4. What will be your charge if you scrape electrons from your feet while scuffing across the rug?

A. Negative

B. Neutral

C. Positive

D. Not enough information given

Ans: C. Positive

-You lose electrons from your feet when you cross a rug, you become positively charged.

5. How is food cooked faster using a pressure cooker?

A. The accumulated steam increases the pressure and decreases the boiling point of the liquid.

B. The accumulated steam increases the pressure and increases the boiling point of the liquid.

C. The accumulated steam decreases the pressure and increases the boiling point of the liquid.

D. The accumulated steam decreases the pressure and decreases the boiling point of the liquid.

Ans: B. The accumulated steam increases the pressure and increases the boiling point of the liquid.

-Pressure is created initially by boiling a liquid inside the closed pressure cooker. The trapped steam increase the internal pressure and the boiling point of the liquid.

6. Which of the following is NOT a characteristic of a base?

A. Bitter taste

B. Slippery feeling

C. Able to change litmus from red to blue

D. Reacts with carbonates to produce carbon dioxide

Ans: D. Reacts with carbonates to produce carbon dioxide

-A, B. C are characteristics of a base. Many bases react with acids and precipitate salts.

7. Which of the following statements about acid and base is TRUE?

A. Baking soda is acidic.

B. Both acids and bases conduct electricity.

C. The concept of H_3­O⁺ was introduced by Arrhenius.

D. The end point is reach when the color of the indicator in titration changes.

Ans: B. Both acids and bases conduct electricity.

-Baking soda is a base. Usually, end point of titration is reached when the solution takes on a persisting solid color as in the pink of phenolphthalein indicator. Both acids and bases conduct electricity because acids and bases are ions that dissociate readily.

8. What is the pH of the solution with an [H⁺] of 1.00 x 10^-11?

A. 1

B. 3

C. 7

D. 11

Ans: D. 11

-The number of decimal places in the log is equal to the number of significant figures in the original number. pH = - LOG [H₃O⁺]= -LOG 10^-11=(-11.0)= +11

9. Which of the following is the most acidic?

A. Calamansi juice

B. Carbonated drink

C. Urine

D. Vinegar

Ans:  A. Calamansi juice

-The pH  value of calamansi juice is around 2.1; vinegar is 2.5; carbonated drink is approximately 2.5-4.0; and urine is round 5.5 to 7.0.

10. Acid rain is formed when sulfur oxides react with water in air. It causes lakes and streams decrease in pH which makes it unable to support fish and plant life. Which is the LEAST means of solving this problem?

A. Limestone may be added to the water basins.

B. Neutralize sulfur oxides with basic compounds.

C. Reduction of sulfur emissions from the industrial establishments.

D. Providing absorbent colloidal materials to screen acid rain before hitting the water.

Ans: D. Providing absorbent colloidal materials to screen acid rain before hitting the water.

-Option D does not prevent acid rain at all. It only prevents temporarily the acid rain from penetrating the water.

11. Which of the following would decrease the rate in which a solid dissolves in a liquid?

A. Supersaturating the solution

B. Applying pressure into the solution

C. Grinding the solid into smaller pieces

D. Increasing the temperature of an exothermic reaction

Ans: D. Increasing the temperature of an exothermic reaction

-Increasing the temperature results in a stress on the products side from the additional heat. Le Chatelier’s principle predicts that the system shifts toward the product side in order to alleviate this stress. By shifting towards the reactant side, less of the solid is dissociated when equilibrium is again established, resulting I decreased solubility.

12. Which factors affects the rate of dissolution when powdered sugar dissolves more rapidly than granulated sugar?

A. Application of heat

B.  Nature of solute

C. Particle size

D. Stirring

Ans: C. Particle size

-Granulated sugar is larger than powdered sugar. The larger the molecules of the solution are, the more difficult it is for the solvent molecules to surround bigger molecules.

13. In which factor is the description “like dissolves like” BEST used?

A. Volume

B. Pressure

C. Temperature

D. Nature of solute and solvent

Ans: D. Nature of solute and solvent

-Polar solutes tend to dissolve best in polar solvents while non-polar solutes tend to dissolve best in non-polar solvent.

14. When the production of hydrogen ions in the body is the same as their loss, you are in_________.

A. acid-base balance

B. electricity balance

C. water balance

D. balance diet

Ans: B. electricity balance

-Electrolytes are minerals in the body that have electric charge. These are present in blood, Urine and body fluids. Electrolytes are obtained from the foods we eat and the fluids we drink.

15.What is the mass percent of Na₂SO₄ in a solution made by dissolving 25 g Na₂SO₄ in 225 g H₂O?

A. .01%

B. 1%

C. 10%

D.20%

Ans: C. 10%

-Mass percent =  g solute   x   100                                             25 g      x   100  =  10%        g solution                                                     25 g +225 g

16. What is the mole fraction of 100 g ethanol (C₂H₆O) mixed in 100 g water?(C=12 H=1 O=16)

A. 0.28

B. 2.17

C. 5.56

D.7.73

Ans: A. 0.28

-   C = 2 x 12 = 24                       H = 2 x 1   = 2

H = 6 x 1   = 6                         O = 1 x 16 = 16

O = 1 x 16 = 16                                            18

                    46

100/46= 2.17                            100/18= 5.56

      2.17                  = 0.28

2.17+5.56

17. What is the molarity of the solution containing 1.4 mol of acetic acid (HC₂H₃O₂) in 250 ml of solution?

A. 4.5M

B. 5.6M

C. 6.5M

D. 7.6M

Ans: B. 5.6M

-          mol = mol = M                              1.4mol x 1000 ml = 5.6 M

                 mL      L                                                  250mL     L

18. What is the normality of a 2M solution  of H₃PO₄?

A. 2 N

B. 3 N

C. 5 N

D. 6 N

Ans: D. 6 N

- 2 moles of H₃PO₄   x  3 moles H       = 6 moles H  = 6 N

       1L                       1 mole H₃PO₄             1L

19. When egg yolk is added to oil and water vinegar to make mayonnaise, the egg yolk serves as__________.

A. coagulant

B. emulsifying agent

C. solvent

D. surfactant

Ans: B. emulsifying agent

-Oil and vinegar (water) mixed together when egg yolk is added. The lecithin, which is a protein in the egg yolk, acts as emulsifying agent. Emulsifying agents have regions that associate with the oil regions that associate with vinegar (water). Thus, the emulsifier ( the egg yolk) acts as a bridge between both the oil and the water.

20. Which of the following involves adsorption?

A. Plating the copper on a steel object

B. Adherence of paint to wood surfaces

C. Brown color of the eyes of the Filipinos

D. Remobal of odor inside a refrigerator using charcoal

Ans: D. Remobal of odor inside a refrigerator using charcoal

-adsorption is the process that occurs when gas or liquid solute accumulates on the surdace of a solid ar liquid (adsorbent), forming a molecular or atomic film. Activated carbon, also called activated charcoal is a material with an exceptional high surface are.

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