Chemistry Interview Questions and Answers
Freshers / Beginner level questions & answers
Ques 1. What is the difference between an atom and a molecule?
An atom is the basic unit of an element, while a molecule is a group of atoms bonded together.
Example:
Oxygen (O2) is a molecule composed of two oxygen atoms.
Ques 2. Define pH and its significance in chemistry.
pH is a measure of the acidity or basicity of a solution. It is crucial for understanding chemical reactions and biological processes.
Example:
A solution with a pH of 7 is neutral, like pure water.
Ques 3. What is the difference between an element and a compound?
An element consists of only one type of atom, while a compound consists of two or more different types of atoms chemically bonded.
Example:
Water (H2O) is a compound composed of hydrogen and oxygen.
Ques 4. What is the purpose of a catalyst in a chemical reaction?
A catalyst speeds up a chemical reaction by providing an alternative reaction pathway with lower activation energy.
Example:
Enzymes act as catalysts in biological systems, facilitating metabolic reactions.
Ques 5. Define isotope and provide an example.
Isotopes are atoms of the same element with different numbers of neutrons. Example: Carbon-14 is an isotope of carbon.
Example:
Carbon-14 is used in radiocarbon dating to determine the age of archaeological artifacts.
Ques 6. What is the significance of the periodic table in chemistry?
The periodic table organizes elements based on their atomic number and chemical properties, providing a systematic way to understand and predict element behavior.
Example:
Elements in the same column (group) of the periodic table share similar chemical properties.
Ques 7. Define the terms cation and anion.
A cation is a positively charged ion formed by losing electrons, while an anion is a negatively charged ion formed by gaining electrons.
Example:
Sodium (Na+) is a cation, while chlorine (Cl-) is an anion.
Ques 8. Define the terms 'oxidation' and 'reduction' in redox reactions.
Oxidation involves the loss of electrons, while reduction involves the gain of electrons. Together, they constitute a redox (reduction-oxidation) reaction.
Example:
In the reaction Zn + CuSO4 → ZnSO4 + Cu, zinc (Zn) undergoes oxidation, and copper (Cu) undergoes reduction.
Ques 9. What is the significance of the Avogadro's number?
Avogadro's number (6.022 x 10^23) represents the number of atoms, ions, or molecules in one mole of a substance. It is a fundamental concept in chemistry.
Example:
One mole of water contains Avogadro's number of water molecules, which is approximately 6.022 x 10^23.
Ques 10. Define the term 'stoichiometric coefficient' in a chemical equation.
Stoichiometric coefficients in a chemical equation represent the molar ratios of reactants and products. They indicate the number of moles involved in the reaction.
Example:
In the balanced equation 2H2 + O2 → 2H2O, the stoichiometric coefficients are 2, 1, and 2, respectively.
Ques 11. What is the role of the nucleus in an atom?
The nucleus of an atom contains protons and neutrons. It is responsible for the mass of the atom and determines its identity.
Example:
Carbon-12 has six protons and six neutrons in its nucleus.
Ques 12. What is the difference between an aldehyde and a ketone?
Aldehydes and ketones are organic compounds with a carbonyl group. In aldehydes, the carbonyl group is at the end of a carbon chain, while in ketones, it is within the chain.
Example:
Formaldehyde is an aldehyde, while acetone is a ketone.
Ques 13. Define the term 'polymer' in chemistry.
A polymer is a large molecule composed of repeating structural units called monomers. Polymers can have a linear, branched, or network structure.
Example:
Polyethylene is a polymer composed of repeating ethylene monomers.
Ques 14. What is the purpose of the Rutherford model of the atom?
The Rutherford model describes an atom as a small, dense nucleus surrounded by electrons in orbit. It was a significant advancement in understanding atomic structure.
Example:
In the Rutherford model, most of the atom's mass is concentrated in the nucleus.
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