Question:

An element M crystallises in a body centred cubic unit cell with a cell edge of 300 pm. The density of the element is 6.0 g cm–3. The number of atoms present in 180 g of the element is ______× 1023. (Nearest integer)

Updated On: Jul 4, 2024
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Solution and Explanation

The correct answer is 22
M is body centred cubic, ∴ Z=2
Let mass of 1 atom of M is A
Edge length =300pm
Density =\(6 g/cm^3\)
∴ \(6 g/cm^3=\frac{Z×A}{300×10^{-10^3}}=\frac{2×A}{27×10^{-24}}\)

\(A=81×10^{-24} g\)
Atoms of M=\(\frac{Total \space mass}{Mass\space  of \space one \space atom}\) 
\(\frac{180}{81×10^{-24}}\) 
\(22.22×10^{23}\)
≅ \(22×10^{23}\)

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Concepts Used:

Solid State

Solids are substances that are featured by a definite shape, volume, and high density. In the solid-state, the composed particles are arranged in several manners. Solid-state, in simple terms, means "no moving parts." Thus solid-state electronic devices are the ones inclusive of solid components that don’t change their position. Solid is a state of matter where the composed particles are arranged close to each other. The composed particles can be either atoms, molecules, or ions. 

Solid State

Types of Solids:

Based on the nature of the order that is present in the arrangement of their constituent particles solids can be divided into two types;

  • Amorphous solids behave the same as super cool liquids due to the arrangement of constituent particles in short-range order. They are isotropic and have a broad melting point (range is about greater than 5°C).
  • Crystalline solids have a fixed shape and the constituent particles are arranged in a long-range order.