Question

1) a) What are the Dalton's postulates? (3M))

b) Define Valency. Write it for Carbon and Helium. (2M)

2) a) Differentiate between Boiling and Evaporation. (3M)

b) What is molecule? Give its types. (2M)​

Answer 1

Answer:

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Answer 2

Answer:

1. a) All matter consists of indivisible particles called atoms. Atoms of the same element are similar in shape and mass, but differ from the atoms of other elements. Atoms cannot be created or destroyed. Atoms of different elements may combine with each other in a fixed, simple, whole number ratios to form compound atoms.

b) he valency of helium is 0.

It does not exchange or share electrons to form bonds with any other molecules. Helium has one shell (k) which requires two electrons and helium having two-electron so the outermost shell is completely filled and helium has zero valency. Therefore its valency is taken as zero.while Valency of carbon is 4. The outer electronic configuration of carbon is 2s22p2. Thus, it has 4 valence electrons. It shares these 4 valence electrons to form 4 covalent bonds.

2. a) Evaporation is a normal process that occurs when the liquid form changes into the gaseous form; while causing an increase in the pressure or temperature. Boiling is an unnatural process where the liquid gets heated up and vapourized due to continuous heating of the liquid.

b) A molecule is defined as two or more atoms of the same element different element that are bound together. A molecule may be homonuclear, which means, it consists of atoms of one chemical element, as with oxygen (O2); or it may be heteronuclear, a chemical compound composed of more than one element, as with water (H2O).

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