The equation MgCO3 → MgO + CO2 (Mr=84). Which mass of MgO is formed when 21.0g of MgCO3 are completely decomposed?
💡 Explanation: Moles of MgCO3 = 21/84 = 0.25 mol. Moles of MgO = 0.25 mol. Mass of MgO = 0.25 × 40 = 10.0g.
The diagram shows arrangement of particles changing from closely packed to spaced out. Which change of state is shown?
💡 Explanation: Boiling is the change of state from liquid to gas involving rapid separation of particles.
X-rays are produced when cathode rays strike on:
💡 Explanation: X-rays are produced when high-energy cathode rays (electrons) strike a metal target.
In an experiment a student observes that removing algae from a pond decreases the fish population. This shows that:
💡 Explanation: Algae provide oxygen and food for fish. Removing them decreases the fish population.
Evolution is supported by the presence of homologous structures because:
💡 Explanation: Homologous structures indicate common ancestry as they share similar structural origin despite different functions.
Intensive exercise increases heart rate to supply more oxygen towards the body's muscles. This response shows the coordination between:
💡 Explanation: Increased heart rate and breathing during exercise shows coordination between the respiratory and circulatory systems.
Algae are placed in a group of plant-like Protists because:
💡 Explanation: Algae are classified as plant-like protists primarily because they can perform photosynthesis like plants.
If an insecticide is sprayed in a grassland ecosystem the trophic level directly affected is:
💡 Explanation: Insects are primary consumers. Spraying insecticide would directly affect this trophic level.
In a forest one species of bird diverges into different food sources. Such evolution is inferred as:
💡 Explanation: Adaptive evolution (adaptive radiation) occurs when a species diverges into different forms to exploit different resources.
The process that takes place on the inner membrane of mitochondria is:
💡 Explanation: The electron transport chain occurs on the inner mitochondrial membrane during aerobic respiration.
A Scientist observes a cell with proper ATP production and respiratory activity but unassembled proteins. The organelle most likely dysfunctional is:
💡 Explanation: Ribosomes are responsible for protein synthesis. Dysfunctional ribosomes would result in unassembled proteins.
The non-protein part of a conjugate enzyme if loosely attached is called:
💡 Explanation: A co-factor is a non-protein chemical compound loosely attached to an enzyme that assists its function.
Ahsan felt pain in his throat and was prescribed antibiotics. He feels better after a day. The infection can be caused by:
💡 Explanation: Antibiotics are effective against bacterial infections explaining why Ahsan felt better after taking them.
Sara's mother kept fruits in a storage room and observed a certain fungus growth on decaying fruit. The fungus would be classified as:
💡 Explanation: Saprophytes are organisms that obtain nutrients by breaking down dead or decaying organic matter.
If the checkpoints regulating cell division are altered the person will most likely get:
💡 Explanation: When cell division checkpoints fail cells can divide uncontrollably leading to cancer.