Question:
What is the mass of:
(a) 0.2 mole of oxygen atoms?
(b) 0.5 mole of water molecules?
Answer:
(a) mass = molar mass × number of moles
molar mass of Oxygen atoms = 16g
mass of 0.2 mol of Oxygen atoms = 16 × 0.2 = 3.2g
(b) molar mass of water molecule (H2O) = 2 × 1 + 16 = 18g
mass of 0.5 mole of Water = 18 × 0.5 = 9g
Atoms and Molecules
Q 1.
Define 'formula mass' of a compound.
Q 2.
(i) State the law of constant proportions.
(ii) Show that water illustrates the law of constant proportions.
Q 3.
Magnesium is two times heavier than C-12 atom, what shall be the mass of Mg atom in terms of atomic mass units? (Given mass of C-12 atom = 12u)
Q 4.
Explain with example that law of conservation of mass is valid for chemical reactions.
Q 5.
Who proposed Law of Definite Proportions (or Law of Constant Composition)?
Q 6.
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 (Na
2SO
3)?
Q 7.
What do we call those particles which have more or less electrons than the normal atoms ?
Q 8.
Fill in the blanks:
One mole of water contains ______________ molecules.
Q 9.
What is gram-atomic mass of an element?
Q 10.
Convert 12 g of oxygen gas into moles.
Q 11.
Fill in the blanks:
The atomic mass of sodium is 23. The gram atomic mass of sodium is _________.
Q 12.
What is the chemical symbol for iron?
Q 13.
What is the atomic mass unit?
Q 14.
Fill in the blanks:
The chemical symbol of flourine is ________.
Q 15.
Give four examples of diatomic molecules.
Q 16.
Name one element each which forms diatomic and tetra atomic molecule.
Q 17.
Give one major drawback of Dalton's atomic theory of matter.
Q 18.
How many atoms are there in 0.25 mole of hydrogen ?
Q 19.
Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?
Q 20.
Fill in the blanks:
The chemical symbol of mercury is _________.
Q 21.
Based on type of substance, how molecules are classified?
Q 22.
What is the molecular mass of a substance?
Q 23.
What are ionic compounds?
Q 24.
Define mole. What is its significance?
Q 25.
Find out number of atoms in 15 moles of He.
Q 26.
What is the mass of 0.2 mole of oxygen atoms ?
Q 27.
Calculate the mass of 3.011 x 10
atoms of carbon
Q 28.
If 16 g of oxygen contains 1 mole of oxygen atoms, calculate the mass of one atom of oxygen.
Q 29.
What is the law of conservation of mass?
Q 30.
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?
Q 31.
Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
Q 32.
Name the element having following Latin names
(i) Stibium
(ii) Cuprum
(iii) Argentum
(iv) Natrium
(v) Stannum
(vi) Wolfram
(vii) plumbum
(viii) Kalium
Q 33.
What is the significance of a chemical symbol?
Q 34.
What is relative atomic mass of an element? How it is related to atomic mass unit?
Q 35.
Define molecule. What are its important properties?
Q 36.
Based on atomicity, how molecules are categorized?
Q 37.
What are polyatomic ions? Give examples?
Q 38.
Name one element which forms diatomic and triatomic molecule.
Q 39.
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)
Q 40.
Dalton's atomic theory says that atoms are indivisible. Is this statement still valid ? Give reasons for answer.
Q 41.
Calculate the molecular masses of the following :
(a) Hydrogen, H
Q 42.
What is an ion ? How is an ion formed ? Explain with the help of two examples of different ions.
Q 43.
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 44.
Fill in the blanks:
Mass of 2 Hydrogen atoms is __________.
Q 45.
If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
Q 46.
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)?
Q 47.
Calculate the mass percentage of Carbon(C) , Hydrogen (H) and Oxygen (O) in one molecule of glucouse (C
6H
12O
6).
(Atomic mass of C = 12u, H = 1u and O = 16u)
Q 48.
What is meant by atomicity ? Explain with two
Q 49.
Calculate the molecular mass of ethanoic acid, CH
Q 50.
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 ?
