Free Scientific Reasoning MCQs with Answers

241. Experiment: A litmus paper was dipped into a lemon juice sample.Observation: The blue litmus turned red.Question: What does this confirm?

• A. Lemon juice is acidic in nature.
• B. Lemon juice is neutral.
• C. It contains basic salts.
• D. Litmus is unreactive with lemon.

Explanation: The correct answer is that lemon juice is acidic in nature. The change in color of the litmus paper from blue to red confirms the presence of an acidic substance. The other options are incorrect because the observation clearly shows an acidic property, not neutrality, basicity, or lack of reaction.

242. Experiment: Dilute sulfuric acid was added to barium chloride solution.Observation: A white insoluble solid formed immediately.Question: What reaction occurred?

• A. Neutralization of acid and base.
• B. Formation of hydrochloric acid.
• C. Formation of barium sulfate as a precipitate.
• D. Combustion of sulfur compounds.

Explanation: The correct answer is the formation of barium sulfate as a precipitate. In this reaction, sulfuric acid reacts with barium chloride to form barium sulfate, which is insoluble and appears as a white solid. The other options are incorrect because they do not align with the observed formation of a precipitate in the experiment.

243. Experiment: A piece of sodium was dropped in water in a trough.Observation: It moved rapidly, producing fizzing and a colorless gas that burned with a pop.Question: What gas was released?

• A. Carbon dioxide from water.
• B. Oxygen from salt decomposition.
• C. Hydrogen gas from sodium-water reaction.
• D. Nitrogen from sodium nitrate.

Explanation: The correct answer is Option C: Hydrogen gas from sodium-water reaction. When sodium is dropped in water, it reacts vigorously to produce hydrogen gas. The fizzing and the pop sound are characteristic of the hydrogen gas being released. Options A, B, and D are incorrect because sodium does not produce carbon dioxide, oxygen, or nitrogen when reacted with water.

244. Experiment: Magnesium ribbon was burned in a jar of carbon dioxide.Observation: A white ash was formed and black carbon was deposited.Question: What does this show?

• A. CO₂ acts as an oxidizing agent.
• B. Magnesium evaporates in CO₂.
• C. Carbon dioxide is neutral gas.
• D. Magnesium can reduce CO₂ to carbon.

Explanation: The correct answer is that Magnesium can reduce CO₂ to carbon. The white ash and black carbon formed in the experiment indicate a chemical reaction between magnesium and carbon dioxide. Magnesium acted as a reducing agent, leading to the reduction of carbon dioxide to carbon. The other options are incorrect because they do not explain the observed results and do not involve a chemical reaction between magnesium and carbon dioxide.

245. Experiment: Concentrated hydrochloric acid was placed in a beaker and a glass rod dipped in ammonia was brought near.Observation: Dense white fumes were observed.Question: What is being formed?

• A. Sulfuric acid vapor reacting with water.
• B. Ammonium chloride due to combination of HCl and NH₃.
• C. Ammonia decomposing in air.
• D. Precipitate of hydrogen gas.

Explanation: The correct answer is Option B: Ammonium chloride due to combination of HCl and NH₃. In the given experiment, the presence of dense white fumes indicates the formation of ammonium chloride resulting from the reaction between hydrochloric acid and ammonia. Option A is incorrect as sulfuric acid is not involved in the experiment. Option C is incorrect as ammonia is not decomposing in air. Option D is incorrect as the observation is not indicative of the formation of hydrogen gas.

246. Experiment: Iron nails were placed in a solution of copper sulfate, and after 30 minutes, they were rinsed and weighed.Observation: Mass increased due to a layer of another metal.Question: What does this confirm?

• A. Displacement reaction where iron replaces copper.
• B. Corrosion by copper ions.
• C. Coating due to evaporation.
• D. Precipitation of salt on iron.

Explanation: The correct answer is Option A: Displacement reaction where iron replaces copper. The increase in mass of the iron nails confirms the formation of a layer of another metal, which occurs as a result of a displacement reaction where iron replaces copper in the copper sulfate solution. The other options are incorrect because they do not explain the observed increase in mass due to the formation of a different metal layer.

247. 48 competitors entered the men's 100 metres freestyle event at this year's Muscan Swimming Championships. They were divided randomly into 6 heats, with the fastest 16 qualifying for the semi-finals.These are the results of the 6 heats.From which heat was there only one qualifier for the semi-finals?

• A. Heat 1
• B. Heat 3
• C. Heat 5
• D. Heat 6

Explanation: The correct answer is Heat 5 because it was the only heat where there was only one qualifier for the semi-finals. In all other heats, there were multiple qualifiers. Heat 1, Heat 3, and Heat 6 had more than one swimmer qualifying for the semi-finals, making them incorrect choices.

248. The ingredients on a jar of mincemeat are in order of content by weight and are as follows:Sugar; Apples (26%); Vine fruit (26%); Candied mixed peel (4%); Vegetable suet; Treacle; Acetic Acid: Mixed spices (0.3%); Citric Acid; Antioxidant (Ascorbic Acid).To the nearest 1%, what is the possible range of sugar content?

• A. 26% to 43%
• B. 26% to 44%
• C. 31% to 43%
• D. 31% to 44%

Explanation: The correct answer is Option B: 26% to 44%. The question provided the order of ingredients by weight in mincemeat, with sugar being the first listed. By considering both the lower limit (26%) and upper limit (44%) of the given range of percentages and rounding to the nearest 1%, we can determine that the possible sugar content falls within this range. The other options either incorrectly exclude one of the limits or start the range at an incorrect percentage.

249. Tom needs to save some money to buy himself a new car. At the start of January there is $400 in his savings account. He is able to add $100 to the account at the end of each month.In April he knows that he will be paid a bonus and have an increase in his salary, so he needs to add $500 to his account at the end of April and then $150 each month of that.Which of the following graphs represents the total money that he will share in his savings account at the end of each month?

• A. A
• B. B
• C. C
• D. D

Explanation: The correct answer is Option A. This graph correctly represents the total amount in Tom's savings account at the end of each month by including his initial balance, monthly contributions, and additional contributions in April and subsequent months. The other options do not consider all the contributions accurately, leading to incorrect representations of the total amount in Tom's savings account.

250. A question-master asks each of four contestants up to 15 questions. The process is repeated again for a second round. The 'score' is the number of questions answered correctly. The scores after each round are announced in ascending numerical order.After the first round of a contest the scores were 8, 10, 11, and 14.After the second round the total scores for the contestants were 13, 18, 20, and 24.What was the largest possible score achieved in the second round of this contest?

• A. 10
• B. 11
• C. 14
• D. 16

Explanation: The largest possible score achieved in the second round of this contest must be higher than any score achieved in the first round. Since the highest score after the first round was 14, the largest possible score in the second round can be at least 15 or higher. Therefore, the correct answer is 14. Options A and B are lower than the highest score in the first round, so they are not the largest possible score. Option D is higher than the highest score in the first round, but it is not the maximum possible score based on the given information.