Q. 124.5( 26 Votes )

# A cubic solid is made of two elements P and Q. Atoms of Q are at the corners of the cube and P at the body-centre. What is the formula of the compound? What are the coordination numbers of P and Q?

Answer :

Given. Atoms of Q are the corners of the cube and P at the body- centre

Therefore, Number of atoms of Q in one unit cell

Number of atoms of P in one unit cell =1

Therefore, Ratio of P and Q atoms = P:Q = 1:1

Therefore, formula of the given compound = PQ

Since it is bcc

Therefore, coordinate number of P and Q = 8

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An element ‘*X*’ (At. mass = 40 g mol^{–1}) having f.c.c. structure, has unit cell edge length of 400 pm. Calculate the density of ‘*X*’ and the number of unit cells in 4 g of ‘*X*’. (*N _{A}* = 6.022 × 10

^{23}mol

^{–1})

Note : In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

Chemistry - ExemplarThe correct order of the packing efficiency in different types of unit cells is ________.

Chemistry - ExemplarThe edge lengths of the unit cells in terms of the radius of spheres constituting fcc, bcc and simple cubic unit cell are respectively________.

Chemistry - ExemplarA cubic solid is made of two elements P and Q. Atoms of Q are at the corners of the cube and P at the body-centre. What is the formula of the compound? What are the coordination numbers of P and Q?

NCERT - Chemistry Part-I