Q111. The pH scale is a measure of the concentration of which ions in a solution?
Science and Technology: RAS Prelims MCQs
1113 RAS Prelims practice MCQs on science and technology are on this page, in 6 chapters. They cover the basics of everyday science, computers and information technology, defence and space technology in India, genetics, biotechnology and nanotechnology, science and technology policies and government programmes, and recent advances with Indian contributors and indigenisation. Each question has an answer and an explanation.
Practice questions based on the RPSC RAS Prelims syllabus. They follow the exam pattern but are not past-paper questions.
Showing 111–120 of 1113 questions
Browse Science and Technology chapters
Q112. A solution turns blue litmus paper red. Its pH is most likely to be:
Explanation
Litmus paper is a common acid-base indicator used to test the chemical nature of a solution. When blue litmus paper turns red, it indicates that the substance is acidic. On the pH scale, which ranges from zero to fourteen, acidic solutions have values less than seven. Therefore, a pH of three clearly represents an acidic environment capable of producing this specific color change.
Q113. A strong acid is characterized by its ability to:
Explanation
A strong acid is defined by its ability to undergo complete ionization or dissociation when dissolved in water. This means that almost every acid molecule breaks apart to release hydrogen ions into the solution. In contrast, weak acids only partially dissociate, with most molecules remaining intact. Common examples of strong acids include hydrochloric acid and sulfuric acid, which are highly reactive and conduct electricity.
Q114. The reaction between an acid and a base to produce salt and water is known as:
Explanation
Neutralization is a chemical reaction in which an acid and a base react quantitatively with each other to produce a salt and water. During this process, the hydrogen ions from the acid combine with the hydroxide ions from the base to form neutral water molecules. The resulting solution is typically closer to neutral pH, provided the reactants are balanced in their respective strengths.
Q115. Milk of magnesia, commonly used as an antacid, is chemically:
Explanation
Milk of magnesia is a common medicinal suspension used to treat indigestion and heartburn. Chemically, it is known as magnesium hydroxide. As a mild base, it works by reacting with the excess hydrochloric acid in the stomach through a neutralization reaction. This process reduces the overall acidity in the digestive tract, providing relief from the discomfort and irritation caused by acid reflux.
Q116. Consider the following common salts and their chemical names:
I. Baking soda - Sodium bicarbonate
II. Washing soda - Sodium carbonate decahydrate
III. Plaster of Paris - Calcium sulfate hemihydrate
IV. Bleaching powder - Calcium oxychloride
V. Table salt - Potassium chloride
Which of the above pair(s) is/are incorrectly matched?
I. Baking soda - Sodium bicarbonate
II. Washing soda - Sodium carbonate decahydrate
III. Plaster of Paris - Calcium sulfate hemihydrate
IV. Bleaching powder - Calcium oxychloride
V. Table salt - Potassium chloride
Which of the above pair(s) is/are incorrectly matched?
Explanation
Most of the listed salts are correctly matched with their chemical names: baking soda is sodium bicarbonate and bleaching powder is calcium oxychloride. However, common table salt is chemically sodium chloride, not potassium chloride. While potassium chloride is sometimes used as a salt substitute for dietary reasons, it is not the primary component of the standard table salt used globally for seasoning.
Q117. Which acid is naturally present in sour milk or curd?
Explanation
Lactic acid is the organic acid naturally present in sour milk, curd, and yogurt. It is produced when certain bacteria, such as Lactobacillus, ferment the lactose sugar found in milk. This fermentation process increases the acidity of the milk, causing the proteins to coagulate and giving curd its characteristic tangy flavor and thick texture, while also acting as a natural preservative.
Q118. The sting of ants and bees contains which of the following acids, causing pain and irritation?
Explanation
When ants or bees sting, they inject a small amount of formic acid, also known as methanoic acid, into the skin. This chemical is responsible for the sharp pain, redness, and swelling associated with the bite. Because it is an acid, its effects can sometimes be neutralized by applying a mild base, such as baking soda paste, which helps to alleviate the irritation.
Q119. Rainwater is typically considered "acid rain" when its pH drops below approximately:
Explanation
Normal rainwater is slightly acidic, with a pH of about five point six, due to dissolved carbon dioxide forming weak carbonic acid. However, when the pH drops below this level, it is classified as acid rain. This increased acidity is primarily caused by sulfur dioxide and nitrogen oxides from industrial activities reacting with water vapor in the atmosphere to form stronger acids.
Q120. Which of the following salts is formed when a strong acid reacts with a weak base?
Explanation
When a strong acid reacts with a weak base, the resulting salt is classified as an acidic salt. This occurs because the strong acid provides more hydrogen ions than the weak base can effectively neutralize. When such a salt is dissolved in water, it undergoes partial hydrolysis, releasing excess hydrogen ions and resulting in a solution with a pH value of less than seven.Answer key for these questions
| Q | Correct answer |
|---|---|
| 111 | (a) Hydrogen ions (H+) |
| 112 | (d) 3 |
| 113 | (b) Completely dissociate into ions in water |
| 114 | (a) Neutralization |
| 115 | (c) Magnesium hydroxide |
| 116 | (d) V only |
| 117 | (c) Lactic acid |
| 118 | (b) Formic (Methanoic) acid |
| 119 | (c) 5.6 |
| 120 | (c) Acidic salt |
Key facts from Science and Technology
- The RPSC paper is General Knowledge and General Science, so science questions come with a strong dose of applied and recent topics.
- Everyday science questions test the laws and terms of physics, chemistry and biology through examples.
- Defence and space questions pair a missile, satellite or mission with its year and organisation.
- Policy questions ask for the year, the body and the aim of schemes like STIP, the National Quantum Mission and BioE3.
- Health, environment and agriculture are on a separate page, with their own chapters.
Frequently asked questions
How many RAS Prelims practice MCQs are there on Science and Technology?
This page has 1113 practice MCQs on Science and Technology. Each has the correct answer, and most have an explanation.
Which chapters does the science and technology set cover?
Six chapters: basics of everyday science; computers, information and communication technology; defence and space technology in India; genetics, biotechnology and nanotechnology; science and technology policies and government programmes; and recent advances, Indian contributors and indigenisation.
Is science and technology part of the RAS Prelims syllabus?
Yes. The RPSC paper is called General Knowledge and General Science, and its syllabus lists science and technology topics along with environment, health, agriculture and government programmes, so questions can come from any of these areas.
How should I prepare science for RAS Prelims?
Revise the concepts by examples, then learn the missions, schemes and scientists with their year and organisation. Attempt each chapter, read the explanations and keep a list of the facts you missed.