monthly exam

What happens to water molecules during hydrolysis?

• They form hydrogen ions (H⁺) and hydroxide ions (OH^-)

• They remain in the solution without binding to the water

• They form hydrogen bonds with other water molecules

• They turn into hydrogen sulfide

Answer explanation

During hydrolysis, water molecules dissociate to form hydrogen ions (H+) and hydroxide ions (OH-). This process is crucial in many biochemical reactions, making the correct choice about the formation of these ions.

What is the role of oxygen in water molecules?

• Has a lower electronegativity than the hydrogen atom

• The concentration of hydrogen ions (H⁺) decreases

• Electrons of the bond are attracted to the oxygen atom, forming a partial negative charge on the oxygen atom and a partial positive charge on the hydrogen atom

• all answers are correct

Answer explanation

Oxygen in water molecules has a higher electronegativity than hydrogen, attracting the bond's electrons. This results in a partial negative charge on oxygen and a partial positive charge on hydrogen, creating a polar molecule.

What is the p^H value variation in groundwater influenced by?

• Weather

• Rock composition

• Altitude

• Soil composition

Answer explanation

The pH value variation in groundwater is primarily influenced by rock composition, as different minerals can release various ions into the water, affecting its acidity or alkalinity. as calcium carbonate or magnesium carbonate

Cloud pH is affected by which environmental factors?

• Bacteria

• Temperature

• Pressure

• Acidic gases

Answer explanation

Cloud pH is primarily affected by acidic gases, such as sulfur dioxide and nitrogen oxides, which can dissolve in water droplets and lower the pH. Other factors like bacteria, temperature, and pressure have less direct impact.

How would you interpret the role of water in the exchange of materials between living organisms and their environment?

• Water carries materials needed for the production of energy and getting rid of wastes within living organisms.

• Water does not pass from the environment to the inside of the cells of living organisms.

• Water has no effect on the membrane that separates living organisms from their environment.

• The movement of materials between living organisms and their environment is not important for their survival.

Answer explanation

Water is essential for transporting nutrients and waste within living organisms, facilitating energy production and maintaining homeostasis, making it crucial for their survival.

How would you express the importance of the water cycle in nature?

• The water cycle is not a system that can make changes to the Earth's surface.

• The water cycle is not important for the movement of water on Earth.

• The water cycle is a system that can make physical, chemical, and biological changes to the Earth's surface.

• The water cycle does not include processes such as evaporation, rain, transpiration, and respiration.

Answer explanation

The correct choice highlights the water cycle's role in causing physical, chemical, and biological changes on Earth, emphasizing its significance in nature, unlike the other options which incorrectly downplay its importance.

the p^H value of solution of ammonium carbonate may be...................

• 7

• 6

• 8

• zero or 14

Answer explanation

The pH of a solution of ammonium carbonate is typically around 7, indicating it is near neutral. This is because it can act as a weak base and weak acid in solution, balancing the acidity and alkalinity.

What physical property of water causes its density to decrease upon freezing?

• Its low specific heat.

• The decrease in the mass of its molecules upon freezing.

• The amount of salt dissolved in it.

• The pressure inside it.

Answer explanation

The correct choice is 'The decrease in the mass of its molecules upon freezing.' Water expands when it freezes due to the formation of a crystalline structure, which decreases its density, making ice less dense than liquid water.

Which biological process of aquatic organisms depends on dissolved oxygen in water?

• Calcification

• Photosynthesis

• Excretion

• Respiration

What is the role of calcium carbonate in marine organisms shells or skeletons?

• A source of energy

• A building block for shells or skeletons

• A source of oxygen

• A byproduct of respiration

Answer explanation

Calcium carbonate serves as a crucial building block for the shells and skeletons of marine organisms, providing structural support and protection. It is not a source of energy, a byproduct of respiration, or a source of oxygen.