Acids Bases and Salts MCQ Class 7 Quiz

Correct Answer: C. Lemon juice. Lemon juice contains acids, which give it a sour taste.

Correct Answer: C. To prevent accidents and injuries. Safety instructions are designed to protect you from potential dangers in the lab.

Correct Answer: B. Spicy. The text mentions sweet, sour, bitter, and salty tastes, but not spicy.

Correct Answer: A. To identify different types of tastes. The experiment focuses on recognizing different taste categories like sour, bitter, sweet, and salty.

Correct Answer: D. Unripe mango. The text advises caution before tasting any substance, especially those that may be unfamiliar like unripe mango.

Correct Answer: B. They could be harmful or toxic. The text emphasizes the importance of avoiding unknown substances as they could be potentially dangerous.

Correct Answer: D. Following instructions. Adhering to instructions is crucial for maintaining safety and avoiding accidents in the lab.

Correct Answer: A. Exploring the different tastes of common substances. The experiment primarily involves tasting and categorizing substances based on their taste properties.

Correct Answer: C. Umami. The text does not include umami as a taste category.

Correct Answer: B. The presence of acids. Acids are responsible for the sour taste in substances like lemon juice.

Correct Answer: B. A Latin word meaning ‘sour’. The word ‘acid’ is derived from the Latin word ‘acere’, which translates to ‘sour’.

Correct Answer: C. Citric acid in lemons. Natural acids are those found in natural substances like fruits and vegetables.

Correct Answer: A. 7. The pH scale ranges from 0 to 14, with 7 representing a neutral solution.

Correct Answer: A. Lemon juice. Substances with a pH less than 7 are acidic, and lemon juice contains citric acid.

Correct Answer: B. Its acidity or alkalinity. The pH scale measures how acidic or basic a solution is.

Correct Answer: D. Detergent. Detergents are synthetic and not a natural source of acids.

Correct Answer: A. Formic acid. The text states that formic acid is found in ant’s sting.

Correct Answer: D. Oxalic acid. The table in the text lists oxalic acid as a component of spinach.

Correct Answer: A. Acetic acid. Vinegar’s main acidic component is acetic acid.

Correct Answer: B. They feel slippery or soapy. Bases have a characteristic soapy or slippery feel.

Correct Answer: C. Baking soda. Baking soda is a common household base.

Correct Answer: C. Bitter. Bases generally have a bitter taste.

Correct Answer: D. Vinegar. Vinegar is acidic, not basic.

Correct Answer: C. Sodium bicarbonate. Baking soda is chemically known as sodium bicarbonate.

Correct Answer: B. Ammonium hydroxide. Ammonium hydroxide is a base often found in cleaning agents.

Correct Answer: B. Magnesium hydroxide. Milk of magnesia contains magnesium hydroxide as its active ingredient.

Correct Answer: D. They taste sour. Sour taste is a property of acids, not bases.

Correct Answer: B. To remove dirt and grease. Bases are effective in breaking down dirt and grease.

Correct Answer:   C. Potassium hydroxide. Potassium hydroxide is a common base used in soap making.

Correct Answer: B. To identify acids and bases. Indicators help distinguish between acidic and basic solutions.

Correct Answer: C. Phenolphthalein. Phenolphthalein is a synthetic indicator, not a natural one.

Correct Answer: B. Red. Litmus turns red in the presence of an acid.

Correct Answer: A. Yellow to red. Turmeric changes from yellow to red in basic solutions.

Correct Answer: A. Dark pink. China rose turns dark pink in acidic solutions.

Correct Answer: A. By dissolving lime in water. Lime water is made by dissolving calcium hydroxide (lime) in water.

Correct Answer: B. As an indicator for acids. Lime water is used to test for the presence of carbon dioxide, which is acidic.

Correct Answer: C. Litmus. Litmus is extracted from lichens.

Correct Answer: B. Yellow. Turmeric remains yellow in acidic solutions.

Correct Answer: C. China rose indicator. The indicator is extracted from the petals of the China rose flower.

Correct Answer: C. Lichens. Litmus is a natural indicator derived from lichens.

Correct Answer: C. Purple. Litmus solution is naturally purple.

Correct Answer: A. Red. Acids turn blue litmus paper red.

Correct Answer: A. It turns blue. Bases turn red litmus paper blue.

Correct Answer: C. The solution is neutral. A neutral solution will not cause a color change in litmus paper.

Correct Answer: C. Pure water. Pure water has a pH of 7, making it neutral.

Correct Answer: B. To identify whether a solution is acidic or basic. Litmus paper is a simple tool to determine the acidic or basic nature of a solution.

Correct Answer: B. Litmus powder. The text mentions litmus solution and litmus paper, but not litmus powder.

Correct Answer: B. It is more convenient and less messy. Litmus paper is easier to handle and less prone to spills compared to litmus solution.

Correct Answer: B. It is basic. Bases cause red litmus paper to turn blue.

Correct Answer: C. By grinding turmeric with water to make a paste. Turmeric indicator is typically prepared as a paste.

Correct Answer: C. Turmeric paper. Turmeric paper can be used as an alternative to turmeric paste.

Correct Answer: B. Reddish-brown. Turmeric changes to reddish-brown when exposed to a base.

Correct Answer: C. It remains yellow. Turmeric does not change color in acidic solutions.

Correct Answer: B. Soap solution. Soap solutions are basic and would cause the color change in turmeric.

Correct Answer: A. It is readily available in most kitchens. Turmeric is a common household spice, making it easily accessible.

Correct Answer: A. Filter paper soaked in turmeric solution. Turmeric paper is prepared by soaking filter paper in a turmeric solution.

Correct Answer: C. It changes its chemical structure in the presence of a base. The color change is due to a chemical reaction between turmeric and the base.

Correct Answer: D. Detecting the presence of a base in a solution. Turmeric is a good indicator for identifying basic solutions.

Correct Answer: B. The solution is acidic or neutral. Turmeric only changes color in the presence of a base, so the solution could be acidic or neutral.

Correct Answer: A. By crushing the petals and soaking them in hot water. The indicator is extracted from the petals by soaking them in hot water.

Correct Answer: C. Dark pink. Acids cause the China rose indicator to turn dark pink.

Correct Answer: A. Green. Bases cause the China rose indicator to turn green.

Correct Answer: B. The solution is weakly acidic. Magenta indicates a less acidic solution compared to dark pink.

Correct Answer: C. Soap solution. Soap solutions are basic and would cause the indicator to turn green.

Correct Answer: B. It provides a distinct color change for weak acids. China rose indicator can differentiate between strong and weak acids based on the intensity of the pink color.

Correct Answer: D. Blue. The text does not mention a blue color change for China rose indicator.

Correct Answer: D. The solution is a strong acid. A deep magenta color indicates a more acidic solution.

Correct Answer: B. To help extract the color from the petals. Hot water helps in efficiently extracting the pigment responsible for the color change.

Correct Answer: C. Distilled water. Distilled water is neutral and would cause minimal color change in the indicator.

Correct Answer: B. The solution is basic. A green color indicates the presence of a base.

Correct Answer: A. They form a salt and water. The reaction between an acid and a base results in the formation of salt and water.

Correct Answer: C. Neutralization. The reaction between an acid and a base is known as neutralization.

Correct Answer: D. Phenolphthalein. Phenolphthalein is often used to visually indicate the completion of a neutralization reaction.

Correct Answer: B. Colorless. Phenolphthalein remains colorless in acidic solutions.

Correct Answer: A. Pink. Phenolphthalein turns pink in the presence of a base.

Correct Answer: C. The solution becomes neutral. Neutralization results in a neutral solution with a pH of 7.

Correct Answer: B. The solution turns colorless. As the acid neutralizes the base, the pink color of phenolphthalein disappears.

Correct Answer: C. A salt. Neutralization reactions produce salt and water.

Correct Answer: C. Taking an antacid for indigestion. Antacids neutralize excess stomach acid.

Correct Answer: C. It neutralizes the acid in the ant’s sting. Calamine solution contains a base that neutralizes the formic acid injected by ants.

Correct Answer: B. To neutralize excess acidity in the soil. Some soils are too acidic for optimal plant growth, and bases help neutralize this acidity.

Correct Answer: C. By adding basic substances to neutralize the acidic waste. Factory waste often contains harmful acids, which are neutralized before disposal.

Correct Answer: C. Increasing soil acidity. Neutralization aims to reduce acidity, not increase it.

Correct Answer: C. It contains bases that neutralize the acids. Saliva has a slightly basic pH to counteract acids from food and bacteria.

Correct Answer: A. Neutralization. Baking soda reacts with acidic ingredients in the cake batter, producing carbon dioxide gas that helps the cake rise.

Correct Answer: B. To create a neutralization reaction. Vinegar (acetic acid) reacts with baking soda (sodium bicarbonate) in a classic neutralization reaction.

Correct Answer: A. Sodium chloride (NaCl) and water (H₂O). This is a standard neutralization reaction producing salt (sodium chloride) and water.

Correct Answer: B. Ca(OH)₂. Slaked lime, or calcium hydroxide, is a common base used in agriculture.

Correct Answer: A. To reduce pollution and protect the environment. Untreated acidic waste can harm ecosystems and water sources.

Correct Answer: C. Milk of magnesia. Milk of magnesia contains magnesium hydroxide, a base that neutralizes stomach acid.

Correct Answer: C. Bacteria producing acids. Bacteria in the mouth produce acids that can damage tooth enamel.

Correct Answer: B. To neutralize the alkaline venom. Bee stings are alkaline, so acidic substances like vinegar are used to neutralize them.

Correct Answer: B. CaO. Quicklime, or calcium oxide, reacts with water to form slaked lime (calcium hydroxide).

Correct Answer: C. To form a salt and water. The defining characteristic of a neutralization reaction is the formation of salt and water from an acid and a base.

Correct Answer: A. Rain that is acidic due to dissolved pollutants. Acid rain forms when pollutants like sulfur dioxide and nitrogen oxides mix with rainwater.

Correct Answer: B. Burning of fossil fuels. The burning of fossil fuels releases gases that contribute to acid rain.

Correct Answer: C. It harms aquatic life by increasing the acidity of water bodies. Acid rain lowers the pH of water, making it harmful to fish and other aquatic organisms.

Correct Answer: B. It corrodes them. Acid rain can damage structures made of stone, metal, and other materials.

Correct Answer: C. Sulfur dioxide. Sulfur dioxide, released from burning fossil fuels, is a key component in the formation of acid rain.

Correct Answer: B. Reduce emissions from factories and vehicles. Controlling emissions from sources like factories and vehicles is crucial in mitigating acid rain.