EXCERCISE 1(A)
.
1. What is a symbol ? What information does it convey ?
2. Why is the symbol S for sulphur, but Na for sodium and Si
for silicon ?
3. Write the full form of IUPAC. Name the elements
represented by the following symbols :
Au, Pb, Sn, Hg.
4. If the symbol for Cobalt, Co, were written as CO, what
would be wrong with it ?
5. What do the following symbols stand for?
(a) H (b) H (c) 2H (d) 2H,
-6. What is meant by atomicity ? Name a diatomic element.
7. (a) Explain the terms 'valency' and 'variable valency'.
(b) How are the elements with variable valency named ?
Explain with an example.
8. Give the formula and valency of:
(a) aluminate
(b) chromate
(c) aluminium
(d) cupric
9. (a) What is a chemical formula ? (b) What is the
significance of a formula ? Give an example to illustrate.
10. What do you understand by the following terms ?
(a) Acid radical (b) Basic radical
11. Select the basic and acidic radicals in the following
compounds.
(a) MgSO4
(b) (NH4)2SO,
(C) AI (SO4)3 (d) ZnCO3
(e) Mg(OH)2
12. Write chemical formulae of the sulphates of Aluminium,
Ammonium and Zinc.
13. The valency of an element A is 3 and that of element B
is 2. Write the formula of the compound formed by the
combination of A and B. PLEASE TELL ME THE RIGHT ANSWERS
Answers
Answer:
Explanation:
1) The first letter/ first two letters of the Latin/Greek(most time) name of a chemical element is Symbol. ... It conveys the definite identity of chemical element in shorter and scientific way.
2) The symbols for the elements are derived from their Latin and Greek synonyms to avoid confusion due to English words.
For Sodium the symbol is Na derived from Natrium, because the symbol S was already taken for Sulphur so Si is the symbol for Silicon
3) IUPAC : Indian Union of Pure and Applied Chemistry.
Au - Gold
Pb - Lead
Sn - Tin
Hg - Mercury
4) The wrong thing in writing cobalt as CO is that we can't write o as O because O represent Oxygen and symbols representing an element with two letters have first one as capital and next one should be in small letter
5) The number after the element tells how many atoms are there. H2 means two hydrogen atoms.
The number before the element is the number of molecules. 2H2 means two molecules of hydrogen and four hydrogen atoms
So the answer is :
H: 1 atom of hydrogen
H2: 1 molecule of hydrogen
2H: 2 atoms of hydrogen
2H2: 2 molecules of hydrogen
6) Atomicity of an element is the number atoms in a molecule of a substance.
examples of a diatomic element is nitrogen molecule
7)when atom loses electrons from its shell which is next to the valence shell is called variable valency .
the number of electrons lost or gained by an atom is termed as valency .
if an atom loses electron then it will be positive valency and an atom gains in electronic then it is negative valency
8) Formula of:
a) Aluminate =\mathrm{AlO}_{3}
b) Chromate =\mathrm{CrO}_{4}^{-2}
c) Aluminium = Al
d) Cupric = Cu(II)
Valency of:
a) Aluminate = -1
b) Chromate = 2
c) Aluminium = 3
d) Cupric = 2
9)The significance of a chemical formula are :
The chemical formula shows the composition of different element or different atoms in the terms of ratio of any molecules.
The chemical formula of any elements indicate its name in the short term and it is easy to study Chemistry.
For example sodium is a very reactive metal which is indicated as (Na) in the short term.
For example sodium hydroxide is an alkali and it is water soluble base which is indicated as (NaOH) in the short term. It also gives the information of the composition of sodium hydroxide in the term of ratio. In NaOH, one mole of sodium atom, one mole of oxygen atom and one mole of hydrogen atom are present in it. It also contain one atom of sodium one atom of Hydrogen and one atom of Oxygen.
10) acid radical - a radical formed from the removal of hydrogen ions from an acid , they are negative charge
basic radical - ions formed from the removal of hydroxide ions , they are positive charged
11) a) basic Mg++ , acidic SO4--
b) Al +++ , SO4--
c) NH4+ , SO4--
d) Zn++ , CO3--
e) Mg++ , OH-
12) Al2(SO4)3
ZnSO4
(NH4)2SO4
13) the compound formed by the combination of A and B will be A2B3
hope it helps you