Question:
What is the mass of
(a) 1 mole of nitrogen atoms?
(b) 4 moles of aluminium atoms (Atomic mass of aluminium = 27)?
(c) 10 moles of sodium sulphite (Na2SO3)?
Answer:
(a) 1 mol of nitrogen (N) atoms = gram atomic mass of N = 14g
(b) mass = molar mass × number of moles
1 mol of Aluminium (Al) = gram atomic mass of Al = 27g
mass of 4 mols of Al = 4 × 27 = 108g
(c) mass = molar mass × number of moles
molecular mass of sodium sulphite (Na2SO3) =
= 2 × Atomic mass of Na + 1 × Atomic mass of S + 3 × Atomic mass of O
= 2 × 23u + 1 × 32u + 3 × 16u = 46u + 32u + 48u
= 126u
mass of 1 mol of sodium sulphite (Na2SO3) = gram molecular mass or molar mass = 126g
mass of 10 moles of Na2SO3 = 10 × 126g = 1260g
Atoms and Molecules
Q 1.
What is gram-atomic mass of an element?
Q 2.
Fill in the blanks:
The atomic mass of sodium is 23. The gram atomic mass of sodium is _________.
Q 3.
What is the mass of 5 moles of sodium carbonate (Na
) ?(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Q 4.
Fill in the blanks:
According to law of definite proportions, in a chemical substance the elements are always present in __________ proportions by mass.
Q 5.
Define 'formula mass' of a compound.
Q 6.
(i) State the law of constant proportions.
(ii) Show that water illustrates the law of constant proportions.
Q 7.
Give four examples of diatomic molecules.
Q 8.
Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Q 9.
What are the postulates of Dalton's atomic theory?
Q 10.
Which of the following statements is NOT true about an atom?
(a) Atoms are the building blocks from which molecules and ions are formed.
(b) Atoms cannot exist independently.
(c) Atoms are neutral in nature
(d) Atoms combine together to form matter that we can see, feel or touch.
Q 11.
What is the chemical symbol for iron?
Q 12.
If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
Q 13.
How many atoms are there in 0.25 mole of hydrogen ?
Q 14.
Show by means of calculations that 5 moles of CO, and 5 moles of H
do not have the same mass. How much is the difference in their masses ?
Q 15.
(a) Define gram atomic mass of a substance.How much is the gram atomic mass of oxygen ?
(b) How many moles of oxygen atoms are present in one mole of the following compounds ?
(i)Al
(ii) co
2(iii) C1
(iv) H
(p)A1
Q 16.
Fill in the blanks:
The mass of 1 mole of a substance is called its _____________.
Q 17.
What are polyatomic ions? Give examples?
Q 18.
What are ionic compounds?
Q 19.
Define mole. What is its significance?
Q 20.
Who introduced the term 'mole' in chemistry?
Q 21.
What are the building blocks of matter ?
Q 22.
What is meant by atomicity ? Explain with two
Q 23.
Calculate the molecular mass of nitric acid,HNO
Q 24.
Calculate the molecular mass of hydrogen bromide (HBr).
(Atomic masses: H=1; Br= 80 U)
Q 25.
Name the following compounds. Also write the symbols/formulae of the ions present in them :
(a) CuSO
Q 26.
What is an ion ? How is an ion formed ? Explain with the help of two examples of different ions.
Q 27.
What is the difference between a cation and an anion ? Explain with examples. Using this information, write down the formulae of:
(i) Sodium sulphide
(ii) Copper nitrate
Q 28.
Fill in the following blanks :
(a)1 mole Contains...........atoms- molecules or ions of a substance
(b)A mole represents an..........number of Particles of a substance.
(c)60 g of carbon element are...........moles of carbon atoms.
(d) 0.5 mole of calcium element has a mass of..........
(e) 64 g of oxygen gas contains..........moles of oxygen atoms.
Q 29.
If one mole of nitrogen molecules weighs 28 g, calculate mass of one molecule of nitrogen in grams.
Q 30.
Calculate the number of molecules in 4 g of oxygen.
Q 31.
Calculate the mass in grams of 0.17 mole of hydrogen sulphide, H
Q 32.
What is the law of conservation of mass?
Q 33.
Who proposed Law of Definite Proportions (or Law of Constant Composition)?
Q 34.
Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?
Q 35.
Fill in the blanks:
Atomic radius is measured in __________.
Q 36.
Fill in the blanks:
_________ are building block of all matter.
Q 37.
Name the international organization who approves names of elements.
Q 38.
Name the element having following Latin names
(i) Stibium
(ii) Cuprum
(iii) Argentum
(iv) Natrium
(v) Stannum
(vi) Wolfram
(vii) plumbum
(viii) Kalium
Q 39.
What is Formula Unit Mass? How it is different from molecular mass?
Q 40.
How do we know the presence of atoms if they do not exist independently for most of the elements?
Q 41.
What is molar mass?
Q 42.
When 'mole' was chosen internationally standard way to express larger number of chemical units?
Q 43.
What is the mass of:
(a) 0.2 mole of oxygen atoms?
(b) 0.5 mole of water molecules?
Q 44.
Calculate the number of molecules of sulphur (S
8) present in 16 g of solid sulphur.
Q 45.
What is meant by the symbol of an element ? Explain with examples.
Q 46.
The molecular formula of glucose is C
Q 47.
Calculate the molecular masses of the following compounds :
(a) Methanol, CH
Q 48.
Name the elements water is made of. What are the valencies of these elements ? Work out the chemical formula for water.
Q 49.
An element X has a valency of 4 whereas another element Y has a valency of 1. What will be the formula of the compound formed between X and Y ?
Q 50.
Work out the formula for magnesium hydrogencarbonate.
