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Question 1: What color does blue litmus paper turn when it is exposed to an acidic solution?
- Purple
- Yellow
- Green
- Red
Answer: D. Red
Explanation: Acids are substances characterized by their sour taste and their ability to turn blue litmus paper red, which is a standard indicator test used in chemistry laboratories worldwide.
Question 2: Which substance property is described as feeling slippery and tasting bitter?
- Acid
- Pure water
- Base
- Neutral salt
Answer: C. Base
Explanation: Bases are chemically defined by their bitter taste and slippery texture. They are the chemical opposites of acids and turn red litmus paper blue when tested in a solution.
Question 3: What is the pH value of a perfectly neutral solution like pure water?
- 14
- 0
- 7
- 10
Answer: C. 7
Explanation: The pH scale ranges from 0 to 14. A value of 7 is considered neutral, representing a balance where the solution is neither acidic nor basic, such as pure water.
Question 4: What are the two primary products formed during a neutralization reaction between an acid and a base?
- Sugar and oxygen
- Gas and metal
- Acid and metal
- Salt and water
Answer: D. Salt and water
Explanation: A neutralization reaction occurs when an acid and a base react to cancel each other out, resulting in the formation of water and a salt as the final products.
Question 5: What gas is typically produced when an acid reacts with a metal?
- Hydrogen
- Nitrogen
- Carbon dioxide
- Oxygen
Answer: A. Hydrogen
Explanation: When an acid reacts with a metal, the chemical process typically produces a salt and hydrogen gas. This gas can be identified by a characteristic pop sound when ignited.
Question 6: According to the Bronsted-Lowry theory, what is an acid?
- Proton acceptor
- Electron acceptor
- Electron donor
- Proton donor
Answer: D. Proton donor
Explanation: The Bronsted-Lowry theory provides a specific definition for these substances: an acid is defined as a proton donor, while a base is defined as a proton acceptor in reactions.
Question 7: How much does acidity change with each whole number shift on the logarithmic pH scale?
- Tenfold
- Hundredfold
- Twofold
- Fivefold
Answer: A. Tenfold
Explanation: The pH scale is logarithmic, meaning that each whole number change represents a tenfold change in the concentration of hydrogen ions, reflecting a significant difference in acidity or alkalinity levels.
Question 8: What gas is released when an acid reacts with a carbonate or bicarbonate?
- Helium
- Oxygen
- Carbon dioxide
- Hydrogen
Answer: C. Carbon dioxide
Explanation: Acids react with carbonates or bicarbonates to produce a chemical reaction that releases carbon dioxide gas as a byproduct, which is often observed as bubbling or fizzing in mixtures.
Question 9: Which substance is considered amphoteric, acting as both an acid and a base?
- Metal
- Salt
- Sugar
- Water
Answer: D. Water
Explanation: Water is unique because it is amphoteric, meaning it has the chemical ability to act as either a Bronsted-Lowry acid or a Bronsted-Lowry base depending on the specific reaction environment.
Question 10: What sound indicates the presence of hydrogen gas when exposed to a lit splint?
- Hissing
- Whistling
- Cracking
- Popping
Answer: D. Popping
Explanation: The hydrogen gas produced during a metal-acid reaction is highly flammable. When a lit splint is introduced, it reacts quickly, producing a distinct pop sound as it burns away.