Convert into mole.
(a) 12 g of oxygen gas
(b) 20 g of water
(c) 22 g of carbon dioxide.
Mass (in grams) = no. of moles x molecular mass (g/mol)
(a) Molar mass of O2 = 2 x 16 = 32 g/mol
Mass = no. of mole x molar mass
12 = n x 32
n = 12/3 = 3/8
n = 0.375 mole
(b) Given mass = 20 g
Molar mass of H2O = 2 x 1 + 1 x 16
= 2 + 16 = 18 g/mol
Mass = no. of mole x molar mass
20 = n x 18
n = 20/18 = 10/9
n = 1.11 mole
(c) Given mass = 22g
Molar mass of CO2 = 1 x 12 + 2 X 16
= 12 + 32 = 44 g/mol
Mass = no. of moles x molar mass
22 = n x 44
n = 22/44 = ½
n = 0.5. mole
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
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)?
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?
Explain how the human ear works.
When a carpet is beaten with a stick, dust comes out of it. Explain.
Which method is commonly used for improving cattle breeds and why?
Differentiate between striated, unstriated and cardiac muscles on the basis of their structure and site/location in the body.
What is the role of epidermis in plants?
A freely falling object eventually stops on reaching the ground. What happenes to its kinetic energy?
Why will a sheet of paper fall slower than one that is crumpled into a ball?
How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?
How is soil formed?
A certain household has consumed 250 units of energy during a month. How much energy is this in joules?