25 Chemistry Important Questions With Answers
1-What is the atomic number of carbon?
The atomic number of carbon is 6.
2-What is the difference between an element and a compound?
An element is a pure substance made up of only one type of atom, while a compound is a substance composed of two or more different elements chemically combined.
3-What is the formula for water?
The formula for water is H2O, indicating that it consists of two hydrogen atoms bonded to one oxygen atom.
4-What is the pH scale used for?
The pH scale is used to measure the acidity or alkalinity of a solution. It ranges from 0 to 14, with values below 7 being acidic, 7 being neutral, and values above 7 being alkaline.
5-What is the chemical symbol for gold?
The chemical symbol for gold is Au, derived from its Latin name “aurum.”
6-What is an exothermic reaction?
An exothermic reaction is a chemical reaction that releases heat energy to the surroundings.
7-What is Avogadro’s number?
Avogadro’s number is 6.022 x 10^23, and it represents the number of particles (atoms, molecules, or ions) in one mole of a substance.
8-What is the difference between an acid and a base?
Acids are substances that release hydrogen ions (H+) in aqueous solutions, while bases are substances that release hydroxide ions (OH-) or accept hydrogen ions.
9-What is the chemical formula for methane?
The chemical formula for methane is CH4, representing one carbon atom bonded to four hydrogen atoms.
10-What is the Law of Conservation of Mass?
The Law of Conservation of Mass states that mass is neither created nor destroyed in a chemical reaction. The total mass of the reactants is equal to the total mass of the products.
11-What is the function of a catalyst in a chemical reaction?
A catalyst increases the rate of a chemical reaction by lowering the activation energy required for the reaction to occur. It remains unchanged at the end of the reaction.
12-What is the difference between an endothermic and an exothermic reaction?
An endothermic reaction absorbs heat energy from the surroundings, while an exothermic reaction releases heat energy to the surroundings.
13-What is the chemical formula for sulfuric acid?
The chemical formula for sulfuric acid is H2SO4, indicating that it consists of two hydrogen atoms, one sulfur atom, and four oxygen atoms.
14-What is the periodic table?
The periodic table is a tabular arrangement of chemical elements based on their atomic number, electron configuration, and recurring chemical properties.
15-What is the difference between a physical change and a chemical change?
A physical change only alters the physical properties of a substance without changing its chemical composition, while a chemical change results in the formation of new substances with different chemical properties.
16-What is the formula for calculating density?
Density is calculated by dividing the mass of an object by its volume. The formula is: Density = Mass / Volume.
17-What is the difference between an isotope and an ion?
Isotopes are atoms of the same element with different numbers of neutrons, while ions are atoms or molecules that have gained or lost electrons, resulting in a net positive or negative charge.
18-What is the chemical formula for table salt?
The chemical formula for table salt is NaCl, indicating that it consists of one sodium atom bonded to one chlorine atom.
19-What is the role of enzymes in chemical reactions?
Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy required for the reaction to occur. They remain unchanged after the reaction and can be reused.
20-What is the difference between a physical property and a chemical property?
A physical property can be observed or measured without changing the substance’s chemical composition, such as color, density, or melting point. A chemical property describes how a substance interacts with other substances and undergoes chemical changes.
21-What is the difference between an exergonic and an endergonic reaction?
An exergonic reaction releases energy to the surroundings, while an endergonic reaction absorbs energy from the surroundings.
22-What is the law of conservation of energy?
The law of conservation of energy states that energy cannot be created or destroyed in a chemical or physical process. It can only be converted from one form to another.
23-What is the chemical formula for glucose?
The chemical formula for glucose is C6H12O6, indicating that it consists of six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.
24-What is oxidation and reduction in a chemical reaction?
Oxidation is the loss of electrons or an increase in oxidation state, while reduction is the gain of electrons or a decrease in oxidation state. Together, they form redox (reduction-oxidation) reactions.
25- What is the difference between a homogenous and a heterogeneous mixture?
A homogeneous mixture has a uniform composition and appears the same throughout, such as a solution. A heterogeneous mixture has a non-uniform composition, and its components can be visibly distinguished, like a suspension or a mixture of oil and water.
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