Some Basic Concepts Of Chemistry Test 4

Formula Mass is generally used for ionic compounds which do not contain discrete molecules, but ions as their constituent units.
The formula mass of a substance is defined as the sum of the atomic masses of constituent atoms in an ionic compound.

Chemical Formula for Ionic Compounds:

Copper is a chemical element with symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity.

Mixtures having a uniform composition throughout their body are known as Homogeneous Mixture.
Example: Mixture of salt and water, a mixture of sugar and water, air, lemonade, soda water, etc.

Water is a compound:

• Its constituents hydrogen and oxygen are present in a fixed ratio, i.e., 2:1 (H₂O).
• Its properties are different from its constituent elements (hydrogen and oxygen).
• Its constituents cannot be separated by simple physical means but require chemical methods.
• Water has a fixed boiling point, which is different from that of both hydrogen and oxygen.

Arsenic is a chemical element with the symbol As and atomic number 33.
Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal.
Arsenic is a metalloid. It has various allotropes, but only the gray form, which has a metallic appearance, is important to the industry.

A pure substance is a substance in which only one type of atom or molecule is present.
Example: Water, Sulphur, Sucrose(pure), Helium, etc.
Thus, a pure substance can only be an element or a compound.

Mixture and a compound both follow the law of conservation of mass so their weight equals to the sum of mass of their components.

1 picometer = 10^-12 m
1 nanometer=10^-9 m
So, 1 picometer = 0.001 nanometer .
From this we get 1 nanometer= 1000 picometer.

Hence, the correct answer is Option A.

Air is a mixture.
When we combine more than one type of element, known as a mixture.
The different percentages are showing that these other elements are present.

Distilled water is the pure form of water with no impurities present in it; others are the mixture of two or more components.