Which has more number of atoms, 100 grams of sodium or 100 grams of iron (given, atomic mass of Na = 23 u, Fe = 56 u)?
Atomic mass of sodium = 23 u
Gram atomic mass of sodium = 23 g
1 mole or 23 g of sodium has = 6.022 x 1023 atom
100 g of sodium has = 6.022x1023 / 23 x 100
= 2.618 x 1024 atom
Atomic mass of Ison (fe) = 56 u
Gram atomic mass of fe = 56 g
1 mole of fe has = 6.022 x 1023 atom
56 g of fe = 6.022 x 1023 atom
100 g of fe = 6.022 x 1023 / 56 x 100
= 1.075 x 1024 atom
Hence, 100 gram of Na has more number of atoms than 100 gram of fe.
Convert into mole.
(a) 12 g of oxygen gas
(b) 20 g of water
(c) 22 g of carbon dioxide.
In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium observations are in agreement with the law of conservation of mass.
sodium carbonate + ethanoic acid → sodium ethanoate + carbon dioxide + water
Write down the formulae of
(i) sodium oxide
(ii) aluminium chloride
(iii) sodium suphide
(iv) magnesium hydroxide
Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
What are polyatomic ions? Give examples.
How many atoms are present in a
(i) H2S molecule and
(ii) PO43- ion?
Calculate the molecular masses of H2, O2, Cl2, CO2, CH4, C2H6, C2H4, NH3, CH3OH.
A 0.24 g sample of compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound by weight.
Calculate the number of aluminium ions present in 0.051 g of aluminium oxide.
(Hint: The mass of an ion is the same as that of an atom of the same element. Atomic mass of Al = 27 u)
Calculate the formula unit masses of ZnO, Na2O, K2CO3, given atomic masses of Zn=65 u, Na=23 u, K=39 U, C=12 u and O=16 u.
Which of the following has more inertia: (a) a rubber ball and a stone of the same size? (b) a bicycle and a train? (c) a five-rupees coin and a one-rupee coin?
State the universal law of gravitation.
Which of the following are matter?
Chair, air, love, smell, hate, almonds, thought, cold, cold-drink, smell of perfume.
A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the force (Fig. 11.3). Let us take it that the force acts on the object through the displacement. What is the work done in this case?
What is meant by a pure substance?
How does the sound produced by a vibrating object in a medium reach your ear?
What are canal rays?
State any two conditions essential for good health.
How is our atmosphere different from the atmospheres on Venus and Mars?
Who discovered cells, and how?
A mass of 10 kg is at a point A on a table. It is moved to a point B. If the line joining A and B is horizontal, what is the work done on the object by the gravitational force? Explain your answer.
Which of the following materials fall in the category of a “pure substance”?
(a) Ice
(b) Milk
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
(f) Mercury
(g) Brick
(h) Wood
(i) Air.
In what direction does the buoyant force on an object immersed in a liquid act?
Under which of the following conditions are you most likely to fall sick?
(a) when you are taking examinations.
(b) when you have travelled by bus and train for two days.
(c) when your friend is suffering from measles.
Why?
What would happen to the life of a cell if there was no Golgi apparatus?
Name A,B,C,D,E and F in the following diagram showing change in its state
Which organisms are called primitive and how are they different from the so-called advanced organisms?
How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?
What are the differences between the mass of an object and its weight?
Write a note on how forests influence the quality of our air, soil and water resources.