Is Matter Around Us Pure — Science STD 9 — Question

Calculate the number of moles present in a drop of chloroform (CHCl₃) weighing 0.0239g.
(Atomic masses: C = 12u; H = 1u; Cl = 35.5u)

A certain species X has 17 protons, 18 electrons and 20 neutrons.

1. What is such a particle called?
2. What is the mass number of X?
3. What is the atomic number of X?

Name the scientist who studied the movement of pollen grains suspended in water through a microscope. What is this phenomenon known as?

Draw a labeled diagram of the experimental set-up to demonstrate the sublimation of ammonium chloride.

The ‘sea-water’ can be classified as a homogeneous as well as heterogeneous mixture. Comment.

Which method is better for recovering sugar from sugar solution: evaporation or crystallization? Give reason for your answer.

The ratio of the radii of hydrogen atom and its nucleus is ~ 10. Assuming the atom and the nucleus to be spherical,

 If atom is represented by planet earth ‘R e’ = 6.4 × 10m, estimate the size of the nucleus.

How are particles of matter affected with increasing or reducing pressure at a given temperature?

An oxide of nitrogen is found to contain nitrogen and oxygen combined together in the ratio of 7: 16 by mass. Derive the formula of the oxide and name it.

In an atom first four shells (K, L, M, and N) are completely filled. Then what is the total number of electrons in that atom?