Question

Which one of the following statements is not correct? This question has multiple correct options.
a.) The unit of surface tension is dynes/cm.
b.) The unit of viscosity coefficient of a liquid are "poise"
c.) CsCl crystallises in a body-centred cubic type of lattice.
d.) The coordination number of ${{\text{S}}^{2-}}$in ZnS is 6

Answer 1

Hint: To find out the statement that is not correct, we have to check each option. We should know about surface tension and viscosity to check its unit. We should also know about CsCl structure. We should know about coordination numbers.

Complete step by step solution:
To find out the incorrect statement we should check the statement present in option.
The unit of surface tension are dynes/cm
We should know about surface tension to check its unit. We should know that it is the property of liquid surfaces to shrink into the minimum surface area possible. From this we can say that the SI unit of surface tension is a Newton per meter. So, now we can say that this statement is incorrect.
The unit of viscosity coefficient of a liquid is "poise".
We should know about viscosity. We should know that viscosity is the resistance of a fluid (liquid or gas) to a change in shape, or movement of neighbouring portions relative to one another. Or we can say that viscosity denotes opposition to flow. It is a correct statement.
CsCl crystallises in a body-centred cubic type of lattice.
We will discuss the structure of CsCl. We should know that CsCl has a cubic structure and the Cs (or Cl) ions are at the eight corners of the cube and the Cl (or Cs) sit are at the centre of the cube. From this we can say that it is not a body-centred lattice. To be Body centred, it requires the same ion to occupy the edges and centre. From this we can say that it is an incorrect statement.

The coordination number of ${{\text{S}}^{2-}}$ in ZnS is 6
We should know that in zinc blende structure (ZnS), sulphide ions are face-centred and zinc is present in alternate tetrahedral voids. Formula is ZnS. Coordination number of Zn is 4 and that of sulphide is 4. So, from this we can say that this statement is incorrect.
From the above discussion we can say that the statement present in option A, option C and option D are incorrect.

Note: We should note that viscosity is the thickness of a fluid, where water has a low viscosity and honey has a high viscosity. Viscosity is the measure of resistance of a fluid to flow. A fluid that is highly viscous has a high resistance (like having more friction) and flows slower than a low-viscosity fluid.