Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Class 9

The Latin name of Silver is Argentum. The symbol of Silver is Ag.

Fixed number of atoms or molecules present in gram atomic mass of an atom or molecules is 6.022 × 10²³.Thisnumber is known as Avogadro constant.

Gram atomic mass of He = 4u
Therefore 52 g of He contains : 
= 52 / 4 
= 13 moles

C is the correct option.a negatively charged ion, i.e. one that would be attracted to the anode in electrolysis.
A. Magnesium (+2)
B. Sulphate (-2)
C. Oxalate (-2)
D. Ammonium(+1)
Hence, only B and C are Anions.

One mole of carbon contains6.022 × 10²³atoms of carbon. The number of particles present in 0.01 mole of carbon = 6.022 × 10²³×0.01=6.022 × 10²¹atoms.

Phosphorus is tetra-atomic. Each molecules of phosphorus contain 4 atoms.

Atomic mass of Magnesium is 12 and Sulphur is 16. Therefore, the ratio of Magnesium ans Sulphur by mass is 12:16 = 12/16 = 3:4.

The mass of one mole of CaCO₃ is equal to 100 g. one mole of is equal to 6.022 × 10²³ions. Therefore, mass of 3.01×10²³ ions = 50 g

98.07848 g mol

The formula for sulfuric acid is H2SO4. The molar mass of sulfuric acid is 98.07848 g mol.

Atomic mass of Sulphur is 32 u and atomic mass of Carbon is 12 u. So, mass of Sulphur is 32/12 times heavier than Oxygen. = 8/3 times.

Gram atomic mass of an element and the gram molecular mass of a compound contain the same number of molecules, which is equal to6.022×10²³molecules.

Definition of a mole:
- The correct definition of a mole is option B: It contains 6.022×10^23 atoms of a given substance.
Explanation:
- The mole is a unit of measurement used in chemistry to represent a specific amount of a substance.
- It is defined as the amount of a substance that contains the same number of entities (atoms, molecules, ions, etc.) as there are atoms in 12 grams of carbon-12.
- The number of entities in a mole is known as Avogadro's number, which is approximately 6.022×10^23.
- Therefore, a mole represents a specific quantity of a substance, regardless of its atomic or molecular mass.
- The correct definition of a mole is that it contains 6.022×10^23 atoms of a given substance, as stated in option B.
Incorrect options:
A. It is equal to the gram atomic mass of the substance:
- This is not the correct definition of a mole. The gram atomic mass is the mass of one mole of atoms of an element, but it does not define what a mole is.
C. It is equal to the gram molecular mass of the substance:
- This is not the correct definition of a mole. The gram molecular mass is the mass of one mole of molecules of a compound, but it does not define what a mole is.
D. It contains 6.022×10^23 molecules of a given substance:
- This statement is incorrect because a mole can contain atoms, molecules, ions, or any other entities, not just molecules.