Test: Laws of Chemical Combination (April 18) - NEET MCQ

Chemical reactions involve merely the combination, separation, or rearrangement of atoms and that during these processes atoms are not subdivided, created, or destroyed.

Avogadro's law states that, "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules". For a given mass of an ideal gas, the volume and amount (moles) of the gas are directly proportional if the temperature and pressure are constant.

Law of Definite Proportions:

1. The law of definite proportions was given by French chemist Joseph Proust in 1799.

2. The law of definite proportions is also known as the law of definite or fixed proportion.

Law of definite proportions or Proust's law states that a chemical compound always contain the same proportion of elements by mass.
Although the law holds good for a large no. of cases, it is not universally true. It's not true in the case of non - stoichiometric compounds.

The law of definite proportions, also known law of definite composition, states that regardless of the amount, a pure compound always contains the same elements in the same proportions by mass. Law of multiple proportions, also known as Dalton s Law, states that when one element combines with another to form more than one compound, the mass ration of the elements in the compounds are simple whole numbers of each other.

Atoms are composed of particles called protons, electrons and neutrons. Protons carry a positive electrical charge, electrons carry a negative electrical charge and neutrons carry no electrical charge at all. The protons and neutrons cluster together in the central part of the atom, called the nucleus, and the electrons 'orbit' the nucleus. A particular atom will have the same number of protons and electrons and most atoms have at least as many neutrons as protons.

Law of Definite Proportions
The discovery that mass was always conserved in chemical reactions was soon followed by the law of definite proportions, which states that a given chemical compound always contains the same elements in the exact same proportions by mass. As an example, any sample of pure water contains 11.19%11.19% hydrogen and 88.81%88.81% oxygen by mass. It does not matter where the sample of water came from or how it was prepared. Its composition, like that of every other compound, is fixed.

The Law of Conservation of Mass (or Matter) in a chemical reaction can be stated thus:
In a chemical reaction, matter is neither created nor destroyed.
It was discovered by Antoine Laurent Lavoisier (1743-94) about 1785. However, philosophical speculation and even some quantitative experimentation preceeded him. In addition, he was certainly not the first to accept this law as true or to teach it, but he is credited as its discoverer.

The correct answer is Option B.
The chemical reaction will be:
NaHCO₃ + CH₃COOH →CH₃COONa + H₂O + CO₂
molar mass:
NaHCO₃ = 84
CH₃COOH=60
CH₃COONa=82
CO₂ =44
84gNaHCO₃ + 60gCH₃COOH → 82gCH₃COONa + 44gCO₂
Moles of NaHCO₃ = 6.3/84= 0.075
Moles of CH₃COOH = 15/60= 0.25
∴NaHCO₃ is the limited reagent.
Moles of CO₂ formed = 0.075
Weight of CO₂ = 0.075×44 = 3.3g

20 g of zinc sulphate

x = (20 * 22.65)/100

x = 4.53g