CL9:Chemistry_SA-2_Important Questions

Questions:

1) State the postulate of Dalton’s atomic theory which can explain the law conservation of mass? (mark-2)

2) Write the names of three elementary particles which constitue atoms? (mark-1)

3) Write the symbols of :         (mark-2)

a) Lead     b) Boron

4) Electrons attribute negative charge, protons attribute positive charge. An atom has both but why there is no charge?  (mark-1)

5) Write molecular mass of following: (mark-3)

a) Chlorine gas  b) Ammonia gas

c) Sulphur trioxide gas.

(Given At. Mass — Cl- 35.5u , N- 14u , H- 1u , S- 32u , O- 16u)

6) Write the names of following compounds:     (mark-3)

a) Ca(OH)2   b) Mg(NO3)2  c) (NH4)2 SO4  d) NaCl

7) Define each of the following and also give example of each.  (mark-3)

a) Atomic Number  b) Mass Number  c) Isotopes  d) Isobars

8) Write the chemical formula of the following:   (mark-3)

a) Calcium Oxide b) Magnesium Oxide

c) Aluminium Hydroxide.

9) What will be the composition of the nucleus of the atom of an element with atomic no. 19 and mass no. 39? Also write its electronic configuration.(mark-3)

10) How many grams of Sodium will have the same no. of atoms as 6 grams of magnesium. (Given: Na- 23u , Mg – 24u)  (mark-3)

10) There are two elements A and B with At.No. are 13 and 14 respectively. And their At. Mass are equal.Find the no. of subatomic particles in each of these elements. What is the relationship between two? (mark-3)

11) Define the term valency. How it is different from valence electrons?Find the valency of Oxygen and Florine.   (mark-3)

12)(i)Name the scientists who discovered neutrons?  (mark-3)

(ii)State the charge and mass of a neutron.

(iii)Where is neutron located in an atom?

13) Helium atom has an atomic mass of 4u and two protons in the nucleus. How many neutrons does it have?   (mark-3)

14)(i) Why does Helium have zero valency?   (mark-2)

(ii) Name the scientist and his experiment to prove that nucleus of an atom is positiely charged. (mark-3)

15)(i) Calculate the molecular mass of molecule of water. (mark-2)

(ii) Find the no. of molecule present in 9g of water. (mark-2)