Unit-3: Basic concepts of chemistry Flashcards
What is chemistry?
Chemistry is the study of matter, its properties, and the changes it undergoes.
Name two everyday applications of chemistry.
Cooking and cleaning.
Mention one role of chemistry in environmental science.
Solving issues like pollution and climate change.
How does chemistry contribute to medical advancements?
Through the development of medicines, diagnostics, and surgical materials.
Who proposed the atomic theory in 1808?
John Dalton.
What are atoms according to Dalton’s atomic theory?
Indivisible particles of matter.
According to Dalton, how do atoms of different elements differ?
They differ in mass and properties.
What happens to atoms during chemical reactions, according to Dalton’s theory?
They are rearranged but not created or destroyed.
Name one limitation of Dalton’s atomic theory.
Atoms are divisible into subatomic particles (protons, neutrons, electrons).
Define atomic mass.
The weighted average mass of all isotopes of an element, compared to 1/12th the mass of a carbon-12 atom.
What is the atomic mass unit (amu)?
A unit used to express atomic and molecular masses.
Calculate the molecular mass of H₂O.
Molecular mass of H₂O = (2 × 1 u) + (1 × 16 u) = 18 u.
What is a mole in chemistry?
A unit representing 6.022 × 10^23 particles.
What is the molar mass of H₂O?
18 g/mol.
How many particles are present in 1 mole of any substance?
6.022 × 10^23.
If 2 moles of H₂ are used, how many molecules of H₂ are present?
2 × 6.022 × 10^23 molecules.
What is an empirical formula?
The simplest whole-number ratio of atoms in a compound.
Give an example of an empirical formula.
CH₂O (for glucose).
What is a molecular formula?
The exact number of atoms of each element in a molecule.
How is the molecular formula related to the empirical formula?
Molecular Formula = n × Empirical Formula.
If the molecular mass of glucose is 180 u, and the empirical formula mass is 30 u, find n.
n = Molecular Mass / Empirical Formula Mass = 180 / 30 = 6.
Define a chemical reaction.
A process where reactants are converted to products.
Write a balanced chemical equation for the formation of water.
2H₂ + O₂ → 2H₂O.
What is stoichiometry?
The calculation of reactants and products in a chemical reaction based on the law of conservation of mass.
In the reaction 2H₂ + O₂ → 2H₂O, what is the molar ratio of H₂ to O₂?
2:1.
If 4 grams of H₂ are used, how many moles of H₂ are there?
Moles of H₂ = Mass / Molar Mass = 4 / 2 = 2 moles.
How many grams of O₂ are required to react with 2 moles of H₂?
1 mole of O₂ is required (molar mass = 32 g/mol), so 32 grams.
How many moles of H₂O are produced if 2 moles of H₂ react completely?
2 moles of H₂O.
