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Abhishek Malhotra asked a question
Subject: Science, asked on on 11/2/13

write 5-6 differences between isobars and isotopes in a tabular form .
Saarah Huda asked a question
Subject: Science, asked on on 16/1/12

how to find valency of an element?
Saket Jha asked a question
Subject: Science, asked on on 12/1/13

what were the drawbacks of thomson model of atom
Yadhukrishna asked a question
Subject: Science, asked on on 21/2/13

Calculate the number of molecules in 8g of Oxygen ?
Lisby Saji & 1 other asked a question
Subject: Science, asked on on 29/9/14

find the valency of sulphur .[atomic no.=16
Alisha Saluja & 1 other asked a question
Subject: Science, asked on on 27/1/13

what are canal rays ?
Hari Krishnan asked a question
Subject: Science, asked on on 8/3/13

5 examples of isotopes and 5 examples of isobars
Nikhita Dharmavaram asked a question
Subject: Science, asked on on 26/11/11

 What is the valency of copper?
Nupur Thakur & 1 other asked a question
Subject: Science, asked on on 11/10/13

EXPLAIN THE LAW OF CONSERVATION OF MASS WITH AN EXAMPLE ?
Gagan Malik asked a question
Subject: Science, asked on on 13/6/10

Compare the properties of electrons, protons and neutrons.
Dalen & 6 others asked a question
Subject: Science, asked on on 3/7/15

what are the application of isotopes
Aqeel Abdul Rahman asked a question
Subject: Science, asked on on 9/3/13

What are the drawbacks of Rutherfords atomic model?
Aman Kumawat asked a question
Subject: Science, asked on on 7/1/12

Q.1. How many molecules are present in

(a) 9 grams of water

(b) 17 grams of amonia

Q.2. Calculate the number of moles in 17 grams of H2O2

Q.3. Show that 12 grams of carbon-12 contains 6.023 x 1023 atoms of 12C

Q.4. What is the mass of one atom of hydrogen ?

Q.5. How many moles of Mg atoms are there in 100 grams of magnesium ?

Q.6. Neon gas consist of single atoms. What mass of neon contains 6.023 x 1023 atoms ?
Alisha Saluja asked a question
Subject: Science, asked on on 22/2/13

difference between electrons protons and neutrons...also find the relation between the three
Vrinda Ojha asked a question
Subject: Science, asked on on 19/11/12

 Who discovered proton? Golstein or Rutherford?
Vidit Goyal asked a question
Subject: Science, asked on 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
chloride
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
168X
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 :
X Y
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
23
.
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
X Y
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
23
atoms of oxygen (iii) 6.022×10
24
molecules of oxygen (Given atomic mass of 0=16u; No. of molecule=6.022×10
23
per mole
15. S
-2
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
23
per mole
17. Calculate the number of moles present in (i) 60g of calcium (ii) 3.011×10
23
number of oxygen atoms
(Given that Ca = 40u ; Avogadro number= 6.022×10
23
)
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
23
)
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
32
S16 ,
16O8)
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=
6.022×10
23
) (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
-2
)
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
2
)
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
22
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.)
Anjali Thakur asked a question
Subject: Science, asked on on 17/5/12

Q1 Tabulate name of elements,their latin names and symbols.
Pooja Ravikumar asked a question
Subject: Science, asked on on 5/3/13

what is the difference between sodium ion and sodium atom ?
Rohan Asrani asked a question
Subject: Science, asked on on 9/1/12

explain the rutherford's gold foil experiment with the help of diagram?
Harshita Sharma asked a question
Subject: Science, asked on on 25/2/12

what is electrovalency and covalency
Michio Kaku & 1 other asked a question
Subject: Science, asked on on 4/5/13

(a) What are isobars? Give one example. (b) Write any two uses of isotopes

Write two differences between isobars and isotopes.
Vipin Beniwal asked a question
Subject: Science, asked on on 20/11/14
Ions are more stable than atoms , Give reason ?
Siddharth Yadav asked a question
Subject: Science, asked on on 3/3/12

why is the valency of phosphorus 3 & 5 both ?
Abhinav Kale asked a question
Subject: Science, asked on on 18/2/13

How to learn the 30 elements of modern periodic table Quickly?
Yash Asher asked a question
Subject: Science, asked on on 23/2/12

Calculate the no. of atoms of each element persent in 9.8 g of sulphuric acid, H2SO4. (H=1, S=32, O=16)
Vishal asked a question
Subject: Science, asked on on 25/2/13

what r the rules of distribution of electrons in different shells of an atom.Pls give me all rules of higher classes also.
Yatri Sheth & 1 other asked a question
Subject: Science, asked on on 9/10/14

What is the valency of Aluminium whose atomic number is 13 ? Give reason.
Dharani Dharan & 1 other asked a question
Subject: Science, asked on on 7/6/13

what is the valency of gold, silver and lead and can you explai how we can find the valency of a compound like NH4, SO2, CO3 etc.
Sagar asked a question
Subject: Science, asked on on 18/10/12

what are properties of anode rays x rays cathode rays and alpha particles
Simran Singh asked a question
Subject: Science, asked on on 10/3/11

 wht r d drawbacks of bohr's model of an atom??
Peri & 3 others asked a question
Subject: Science, asked on on 23/2/15

 Give 6 examples of isobars .........
Yash Dev Lamba asked a question
Subject: Science, asked on on 21/1/13

valency of carbon in CH4 , C2H6 , C2H4 , C2H2 ???
jaybhartigupta... asked a question
Subject: Science, asked on on 13/1/11

 discovery of electrons
ANIRUDH99 asked a question
Subject: Science, asked on on 19/3/14

Calculate the percentage of

[a] Water of crystallization in CuSO4.5H2O

[B] Potassium in K2CO3

[c] Oxygen in 22g of CO2

[D] Hydrogen in 36g of water
Hardik Sharma & 1 other asked a question
Subject: Science, asked on on 29/1/14

State 3 characteristics of canal rays.
Aditya Sangani asked a question
Subject: Science, asked on on 26/3/16

​Calculate number of neutrons present in 12 × 1025 atoms of oxygen (8O17). (Given NA = 6 × 1023 atoms)

(A) 1800 (B) 1600 (C) 1800 NA (D) 3200 NA
Aagam Shah asked a question
Subject: Science, asked on on 1/2/13

 State two main postulates of Thomson model of an atom
Shubham Sharma asked a question
Subject: Science, asked on on 4/3/13

 applications and examples of isotopes an isobars ?
Shakshi Gupta asked a question
Subject: Science, asked on on 18/12/13

the description of atomic particles of two elements X and Y is given below:

X Y

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.
Punarv Gangnaik asked a question
Subject: Science, asked on on 10/11/13
  1. Calculate the molecular mass of CaCO3 at mass Ca=40u,C=12u,O=16u
  2. Verify by calculating that
  • 5 moles of CO2 and 5 moles of H2O do have the same mass.
  • 240g of calcium and 240g of magnisium element have a mole ratio of 5:3.at mass H=1u ,Ca=40u,Mg=24u
Angel Anjali asked a question
Subject: Science, asked on on 12/2/12

what is difference between Isotopes, Isobars and Isotones
Sandeep Prasad & 2 others asked a question
Subject: Science, asked on on 27/2/15

give the atomic masses of important element for class 9
Asra Khan asked a question
Subject: Science, asked on on 2/3/13

an element X forms an oxide with formula X2O3

rn

state the valency of X,write the formula of chloride of X and sulphate of X.
Pkborghate asked a question
Subject: Science, asked on on 31/12/11

difference between isotope and isobars
Stebin asked a question
Subject: Science, asked on on 17/3/14

The electronic configuration of potassium(K) is 2,8,8,1 instead of 2,8,9 thogh the M shell can accommodate up to 18 electrons. Explain
Abhishek Pal & 1 other asked a question
Subject: Science, asked on on 10/1/14

who discovered the proton? E. goldstein or rutherford?
Akrity Khetan asked a question
Subject: Science, asked on on 4/7/10

If Z = 3, what would be the valency of the element? Also, name the element.
Namrata asked a question
Subject: Science, asked on on 2/3/13

write three significant features of Bohr's model of an atom.
chetandkumawat... asked a question
Subject: Science, asked on on 24/11/10

Name three feature of rutherford's model
Rithu Babu asked a question
Subject: Science, asked on on 15/2/12

what are cathode rays and anode rays?
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