Q.1 What is the SI unit of amount of a substance? Give its symbol.

Ans: The International System of Units (SI) defines the amount of substance to be proportional to the number of entities present. The SI unit for amount of substance is the mole. It has the unit symbol mol. The proportionality constant is the inverse of the Avogadro constant.

• State Boyle’s law.

Ans: At constant Temperature (T), the Volume (V) of a given mass of gas is inversely proportional to its Pressure (P).

i.e.

Q.2 Give any two factors that would increase the rate of evaporation of a liquid.

Ans: Evaporation takes place when a liquid turn into a gas. Evaporation is also known as vaporization. Vaporization usually happens on the surface of the water.

• Vaporization also depends on factors like:
• Temperature: The rate of evaporation increases with an increase in temperature.
• Surface area: The rate of evaporation increases with an increase in surface area.
• Humidity: The amount of water vapour present in the air is called humidity.

Q.3 What do the following symbols represent?

Mm
Mm
Dam
nm

Ans: Mm symbol represent >> millimolar.

Mm symbol represent >> micro metre

dam symbol represents >>decimetre

The symbol ‘nm’ represents Nanometre. A nanometre is one billionth part of metre.

Q.4 Differentiate between mineral and ore.

Q.5 Explain in which of the following compounds, the chemical bond would have less ionic character:

LiCl or KCl

Ans: On the other end, we have Cl on the second to last column, which means it is a halogen, a non-metal (in fact it is a gas at room temperature). A bond between a metal and non-metal is said to be primarily ionic in nature, or it is said that it has high “ionic character” LiCl would has less ionic character than KCl.

It is because potassium is more reactive than Lithium and more reactive metal have more ionic character So, LiCl have less ionic character.

• X and Y are two completely miscible liquids and the intermolecular forces vary as Y-Y < X-X < X-Y.

Explain—

•  which one of the two liquids will boil at a higher temperature;

•  when the two liquids are mixed, what type of deviations would the solution show from the Raoult’s law.

Ans:

(i) and (ii) both – On mixing A and B, the solution becomes warm.

This means heat released in formation of new bonds between A and B molecules is more than the heat absorbed for the breaking of molecules of A and B.

Therefore, the vapour pressure of the solution is reduced and thus the mixture shows negative deviation from Raoult’s law.

• Give the significance of the four quantum numbers.

Ans: A total of four quantum numbers are used to describe completely the movement and trajectories of each electron within an atom. The combination of all quantum numbers of all electrons in an atom is described by a wave function that complies with the Schrödinger equation.

• What is a colloidal solution? How do true solutions, colloidal solutions and suspensions differ with one another in respect to (a) visibility and (b) settling of particles?

• What is stereoisomerism? Which type of stereoisomerism is shown by 1,2- dichloroethene? Draw the structures of its two isomers and name them.

Ans: Stereoisomers are molecules that have the same molecular formula and sequence of bonded atoms, but differ in the three-dimensional orientations of their atoms in space.

1,2-Dichloroethene, commonly called 1,2-dichloroethylene or 1,2-DCE, is an organochloride with the molecular formula C2H2Cl2. It is a highly flammable, colourless liquid with a sharp, harsh odour. It can exist as either of two geometric isomers, cis-1,2-dichloroethene or trans-1,2-dichloroethene.

• Indicate whether you would expect the entropy of the system to increase or decrease in the following processes. Give reasons for your answer:

Ans: Dry ice is frozen CO2 gas. The freezing temperature at normal sea level air pressure is -78.5 degrees C (-109.3 degrees F) conversion of CO2(g) into dry ice is correct.