Chemistry HSE Exam: Law of Multiple Proportion

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Who proposed the Law of Multiple Proportion?

John Dalton

Define a.m.u (atomic mass unit).

1/12th the mass of a C12 atom

Who proposed the Law of Conservation of Mass?

Antoine Lavoisier

What is the definition of molar mass?

The mass of one mole of a substance in grams Signup and view all the answers

Define 1 mole of a substance.

The amount of substance that contains 6.022 x 10^23 atoms Signup and view all the answers

Define mass percentage and provide the formula to calculate it.

Mass percentage is the percentage of each element present in 100g of a substance. The formula to calculate mass percentage is: Mass percent of an element = (Mass of that element in the compound / Molar mass of the compound) x 100 Signup and view all the answers

What are empirical and molecular formulae? Explain the difference between them.

The empirical formula is the simplest formula which gives only the ratio of different elements present in the compound. The molecular formula is the actual formula that gives the exact number of different elements present in the sample. Signup and view all the answers

Find the number of moles and molecules present in 90g of water.

Number of moles (n) = 90g / 18 = 5 moles. Number of molecules = number of moles x 6.022x10^23 = 5 x 6.022x10^23 Signup and view all the answers

What is the limiting reagent in a chemical reaction?

The limiting reagent, or limiting reactant, is the reagent which limits a reaction or the reagent which is completely consumed in a chemical reaction. Signup and view all the answers

Differentiate between molarity and molality, and provide their respective formulas.

Molarity is the number of moles of solute dissolved per litre of solution, and its formula is Molarity (M) = Number of moles of solute (n) / Volume of solution in litres (V). Molality is the number of moles of the solute present per kilogram (kg) of the solvent, and its formula is Molality (m) = Number of moles of solute / Mass of solvent in kg Signup and view all the answers

What are aromatic compounds characterized by?

Planar structure Signup and view all the answers

What is the key element present in organic compounds?

Carbon Signup and view all the answers

What role does the classification of organic compounds play?

Helps researchers understand their properties and behavior Signup and view all the answers

Name one industry in which organic compounds have various applications.

Pharmaceuticals Signup and view all the answers

What makes aromatic compounds a subclass of organic compounds?

Unique chemical and physical properties Signup and view all the answers

What is the resistance of aromatic compounds to oxidation?

They are generally resistant to oxidation. Signup and view all the answers

Name a type of aromatic compound with one or more alkyl groups attached to a benzene ring and provide an example.

Alkylbenzenes; Example: Toluene Signup and view all the answers

What are some applications of aromatic compounds?

Perfumes and fragrances, medicines, industrial chemicals, and natural products Signup and view all the answers

Provide an example of a polycyclic aromatic hydrocarbon (PAH) and describe its structure.

Coronene; It has five benzene rings arranged in a pentagonal structure. Signup and view all the answers

What is the significance of the sweet or pungent odor of many aromatic compounds?

It is often used in perfumes and other fragrances. Signup and view all the answers