Question

CLASS 9 SCIENCE CHAPTER 2 please answer my question 16 to 20.

16. What is the procedure to obtain........?​

Answer 1

16. by hydrolysis

17.

Explanation:

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Answer 2

16. By increasing the pressure, the air can be compressed. The compressed air is allowed to cool by decreasing its temperature and the air gets liquefied. The liquefied air is allowed to pass into a fractional distillation column. Depending upon their boiling point different gases get separated at different heights.

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An air separation unit is often called an oxygen or nitrogen generator, since its purpose is to extract one or both of these elements from the air. In the distillation process, the air is first passed through a filter that absorbs all the water vapor. Then the cooling process begins. It involves the use of turbines and high-energy refrigeration systems. Carbon dioxide and other trace gases settle out when the temperature reaches each of their sublimation or boiling points. Sublimation describes the change of state directly from a solid to a gas.

When the temperature reaches −200 °C, the liquified mixture is fed through a tube into a vessel that is slightly warmer at the bottom (−185 °C) than it is at the top ( −190 °C). Oxygen liquifies at −183 °C, so it flows out of the flask through a tube in the bottom. Nitrogen turns back into a gas, however, because its boiling point is −196 °C. It flows out through a tube connected to the top of the flask.

17. Fog is different from smoke in the following important ways:

• Both fog and smoke have same dispersion medium (air) but they differ in dispersed phase. In smoke, solid particles are dispersed in air while in fog, liquid particles are dispersed in air.

• Fog is basically condensed water vapor. It isn't a pollutant but reduces visibility. Smoke, on the other hand, is a collection of particles that form by combustion of a material and is a pollutant.

18. Compounds contain two or more different elements.  Water is a molecule because it contains molecular bonds. Water is also a compound because it is made from more than one kind of element (oxygen and hydrogen). If you like, you can say that water is a molecular compound.

19. Given:

Mass of solute = 45g  

Mass of solution = 500g

To find:

Concentration of the solution = ?

Formula to be used:

Mass % of a component = $\frac{Mass\ of\ the\ components\ in\ the\ solution}{Total\ mass\ of\ the\ solution}*100$

Calculation:-

When the given values are substituted in the formula of it gives concentration of the solution which is as follows:

Mass % of a component = $\frac{Mass\ of\ the\ components\ in\ the\ solution}{Total\ mass\ of\ the\ solution}*100$

Mass % = $\frac{45\ g}{500\ g}$

Mass % = 0.09×100

$\boxed{Mass =9}$

Thus the concentration of 45g salt present in 500g of solution is 9.

20. Allow the mixture to be heated, naphthalene powder will get sublimated, get it back by deposition (using cotton ball on top of the funnel).

Common salt won't get sublimated and will remain as a residue.