Question

Science

1. State the laws of chemical combination.
2. Explain Dalton's theory.
3. Write the formula of the following:
(a) sodium hydroxide
(b) calcium chloride
(c) zinc oxide
(d) potassium hydroxide
4. Define mole.
5. What is ion?



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Answer 1

Answer:

1)laws of conservation of mass:- In all chemical and physical changes ,the total mass of the reactant is equal to that of product i.e.,there is no change or decrease in the total mass of the matter.

OR

Mass can neither be created nor be destroyed.

2)laws of constant proportion:-A chemical compound is always found to be mde up of two same elements combined together in a fixed ratio by mass.

E.g, C02------C+02

3)laws of multiple proportion:-when two elements combined to form twonor more compounds,the masses of one of the element which combined with fixed mass of the other element bear a simple ratio to one another.

Eg.,C+0-----;--C0

C+02----C02

4)laws of reciprocal proportion:-The ratio of the masses of two elements A and B which combine separately with a fixed mass of 3rd element either the same or sum of simple multiple of ratio of masses in which A and B combines directly with each other.

5)Guy Lussac's law of gaseous volume:-When gas react together they always do so in volume which bear a simple ratio to one naother and the volume of the product,provided all measurements of volume are done under similar conditions of pressure and temperature.

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Answer 2

1) The laws of chemical combination are -

1. Law of conservation of mass.
2. Law of definite proportions.
3. Law of multiple proportions.
4. Law of reciprocal proportions.
5. Gay Lussac's law of gaseous volumes.
6. Avogadro's law.

2) The concept that matter is composed of very tiny particles was given by Indian and Greek philosophers.

The Greek philosopher Democratus suggested that the ultimate particle of a matter is atom.

The word atom has been derived from the Greek word atomos which means indivisible.

The old ideas were put on a scientific scale by John Dalton in the form of a theory, known as Dalton's atomic theory.

3)

a) NaOH

b) CaCl2

c) ZnO

d) KOH

4) Mole is the unit to measure the amount of substance.

5) It's an atom or group of atoms that bears one or more positive or negative electrical charges.