011-40705070  or  
Call me
Download our Mobile App
Select Board & Class
  • Select Board
  • Select Class
Vidit Goyal , asked a question
Subject: Science , asked on 31/12/12

1.An element ‘X’ forms an oxide with formula X2O3. State the valency of ‘X’ and write the formula of its
2. Define mole. How many grams of sodium will have the same number of atoms as 6 grams of
magnesium ? (Given Na5 23u, Mg5 24 u)
3. You are given an elements . Find out (a) Number of protons, electrons and neutrons in ‘X’ (b) Valency of
‘X’ (c) Write the chemical formula of the compound formed when ‘X’ react with (i) hydrogen, (ii) carbon
4. An elements has mass number 35 and atomic number 17 find (i) the number of neutron in the element,
and (ii) the number of electrons in the outermost shell.
5. Name the anion and cation which constitute the molecule of magnesium oxide
6. Percentage of three elements calcium, carbon and oxygen in a sample of calcium carbonate is given as :
Calcium =40% ; Carbon =12.0% ; Oxygen = 48%
If the law of constant proportion is true, what weights of these elements will be present in 1.5 g of another
sample of calcium. Carbonate ?
(Atomic mass of Ca = 40 u, C = 12 u, O = 16 u)
7. The description of atomic particles of two elements X and Y is given below :
Protons 8 8
Neutrons 8 9
Electrons 8 8
(i) What is the atomic number of Y?
(ii) What is the mass number of X?
(iii) What is the relation between X and Y?
(iv) Which element/elements do they represent?
(v) Write the electronic configuration of X?
(vi) Write the cation/anion formed by the element
8. Which of the following are isotopes and which are isobars?
Argon, Protium, Calcium, Deuterium. Explain why the isotopes have similar chemical properties but they
differ in physical properties?
9.What is the number of molecules in 0.25 moles of oxygen ? Avogadro’s no. 6.02×10
10. Write down the formulae of
(a) sodium carbonate (b) Ammonium chloride (c) Zinc oxide (d) Aluminium hydroxide11.What do the following symbols formulae stand for : (a) 2O (b) O2 (c) O3 (d) H2O (ii) Give the chemical
formulae of the following compounds : (a) Potassium Carbonate (b) Calcium chloride (iii) Calculate the
formulae unit mass of Al2 (SO4)3 (Given atomic mass of Al – 27u, S – 32u, O – 16u)
12. Write the chemical formula of ammonium sulphate.
13. The composition of nuclei of two atomic species X and Y are given below
Protons 17 17
Neutrons 18 20
Find the mass number of X and Y. State the relationship between X and Y
14. Find the mass of the following : (i) 0.5 mole of oxygen gas (ii) 3.011×10
atoms of oxygen (iii) 6.022×10
molecules of oxygen (Given atomic mass of 0=16u; No. of molecule=6.022×10
per mole
15. S
has completely filled K,L and M shells. Find its atomic number.
16. Find the number of particles in each of the following : (i) 0.1 mole of C atoms (ii) 46 g of Na atoms
(Given that Na = 23u ; No. of molecule=6.022×10
per mole
17. Calculate the number of moles present in (i) 60g of calcium (ii) 3.011×10
number of oxygen atoms
(Given that Ca = 40u ; Avogadro number= 6.022×10
18. State one use each of an isotope of (i) uranium , (ii) iodine.
19. The chemical formula of oxide of an element X is X2O5. Write the chemical formula of its chloride.
20. Calculate the number of particles in each of the following : (i) 7 g of Nitrogen molecules (ii) 0.5 mole of
carbon atoms (Given N=14 u ; C=12 u ; Avogadro number= 6.022×10
21. Which of the following compounds have polyatomic ions ? NaOH, NaCl, Na2O, NaNO3
22. Sulphur dioxide (SO2) is a colourless pungent smelling gas and is a major air pollutant. (a) Write the
electronic configuration of its constituent elements „sulphur and Oxygen. (Given, ). (b) Write valency of
Sulphur and Oxygen. (c) Are sulphur and oxygen isotopes of same element. Explain your answer. (Given
S16 ,
23. What is the mass of 0.5 mole of NH3 ? Given Atomic mass of N = 14u, Atomic mass of H = 1u. (c)
Calculate the number of particles in 31 g of P4molecules. Atomic mass of P=31u. ( Avogadro number=
) (d) Find the number of moles in 87g of K2SO4 (Atomic mass of K=39u, S=32u
24. A light and a heavy object have the same momentum. What is the ratio of their kinetic energies ? Which
one has a larger kinetic energy ?
(ii) A ball is dropped from a height of 10m. If the energy of the ball reduces by 40% after striking the
ground, how much high can the ball bounce back ? (g=10 ms
25. Write the names of compounds represented by the following formulae : (i) KNO3 (ii) Al2(SO4)3 (iii) CCl4
(iv) H2S
26. Two boys Ram and Shyam have mass equal to 40 kg each. They start climbing a rope separately and
both reach a height of 6 m. Ram takes 20 seconds and Shyam takes 25 seconds to complete the task. Who
has more power? Explain your answer. (Take g =10 m/s
27. (a) What would be the formula of chloride of ‘X’ if it is a metal and its oxide has the formula XO ? (b)
Write a difference between an atom and an ion. (c) Give an example of each : (i) Triatomic molecule. (ii)
Polyatomic ion. (iii) molecule of a compound (iv) cation (v) an element with valency – 3
28. In an office, a tube light of 40W, a fan of 75 W and a cooler of 150 W are installed. If the appliances are
used for 8 hours per day, find the energy consumed per day in commercial unit.
29. a)Calculate the mass of 0.72 g molecule of CO2. (At mass of C=12 u, O=16 u) (b) Calculate the number of
moles of iron in iron sheet containing 10
atoms of iron.
30. Calculate the molar mass of Nitric acid (HNO3). (Atomic Mass of H=1u, N=14u, O=16u) (b) Calculate
the no. of moles in 270 g of Aluminium. (Atomic mass of Al=27 u) (c) Calculate the mass of 0.5 moles of
Helium gas (Atomic mass He=4u.)


Urvashi Yadav , Meritnation Expert added an answer, on 2/1/13

Due to paucity of time it would not be possible for us to provide the answers to all your queries. We are providing solutions to some your good queries. Try solving rest of the questions yourself and if you face any difficulty then do get back to us.

A-1) Element X = Al ( aluminum)

Oxide of Al - Al2O3

Chloride of Al - AlCl3

A-9) Number of molecules in 0.25 moles of oxygen = 0.25 * 6.023*1023 = 1.505*1023 particles.

A-21) Out of NaOH, NaCl, Na 2 O, NaNO 3 , compound having polyatomic ion is NaNO 3 .

This conversation is already closed by Expert

  • Was this answer helpful?
  • -1
43% users found this answer helpful.
View More
Soumya , added an answer, on 31/12/12
103 helpful votes in Science
  1. The valency of X is 3. The formula is XCl3 .
  • Was this answer helpful?
  • 0
50% users found this answer helpful.