Question:
Fill in the blanks:
The atomicity of sulphur S8 is ________.
Answer:
eight (polyatomic).
Atoms and Molecules
Q 1.
Fill in the blanks:
The atomic mass of sodium is 23. The gram atomic mass of sodium is _________.
Q 2.
What is gram-atomic mass of an element?
Q 3.
What is the chemical symbol for iron?
Q 4.
Define molecule. What are its important properties?
Q 5.
Write the formulae of the following compounds. Also name the elements present in them.
(a) Water
(b) Ammonia
(c) Methane
(d) Sulphur dioxide
(f) Ethanol
Q 6.
Define 'formula mass' of a compound.
Q 7.
Write the chemical symbols of the following:
(i) Gold
(ii) Iron
(iii) Chlorine
(iv) Mercury
Q 8.
Name one element each which forms diatomic and tetra atomic molecule.
Q 9.
(i) State the law of constant proportions.
(ii) Show that water illustrates the law of constant proportions.
Q 10.
Name the international organization who approves names of elements.
Q 11.
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 12.
Fill in the blanks:
The mass of 5 moles of ammonia (NH
3) is __________.
Q 13.
Fill in the blanks:
The chemical symbol of mercury is _________.
Q 14.
Give four examples of diatomic molecules.
Q 15.
What are ionic compounds?
Q 16.
Calculate the number of molecules of phosphorus (P
4) present in 31 gram of phosphorus.
Q 17.
Convert 12 g of oxygen gas into moles.
Q 18.
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 20.
How many atoms are there in 0.25 mole of hydrogen ?
Q 21.
What is the mass of 5 moles of sodium carbonate (Na
) ?(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Q 22.
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 23.
What are polyatomic ions? Give examples?
Q 24.
Write down the names of compounds represented by the following formulae:
(i) Al
2(SO
4)
3 (ii) CaCl
2 (iii) K
2SO
4 (iv) KNO
3 (v) CaCO
3
Q 25.
Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?
Q 26.
Calculate the formula unit masses of ZnO, Na
2O, K
2CO
3, given atomic masses of Zn = 65 u, Na = 23 u, K = 39 u, C = 12 u, and O = 16 u.
Q 27.
Who established the two important laws of chemical combinations?
Q 28.
State Law of constant proportions. Explain with an example.
Q 29.
Fill in the blanks:
According to law of definite proportions, in a chemical substance the elements are always present in __________ proportions by mass.
Q 30.
Fill in the blanks:
The atomicity of sulphur S
8 is ________.
Q 31.
Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
Q 32.
Fill in the blanks:
The mass of 1 mole of a substance is called its _____________.
Q 33.
Which element has the smallest atom in size?
Q 35.
Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Q 36.
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 37.
What is the mass of:
(a) 0.2 mole of oxygen atoms?
(b) 0.5 mole of water molecules?
Q 38.
Calculate the number of molecules of sulphur (S
8) present in 16 g of solid sulphur.
Q 39.
Name the element having following Latin names
(i) Stibium
(ii) Cuprum
(iii) Argentum
(iv) Natrium
(v) Stannum
(vi) Wolfram
(vii) plumbum
(viii) Kalium
Q 40.
Fill in the blanks:
An element has only one type of __________.
Q 41.
Fill in the blanks:
The chemical symbol of flourine is ________.
Q 42.
Based on type of substance, how molecules are classified?
Q 43.
(i) What is the chemical formula of Water molecule?
(ii) What is its atomicity?
(iii) Calculate the ratio of masses of atoms of elements present in water molecule.
(iv) Calculate the ratio by number of atoms of elements present in water molecule.
Q 44.
Write the chemical formulae of the following. Also identify the ions present.
(a) Magnesium chloride
(b) Calcium oxide
(c) Copper nitrate
(d) Aluminium chloride
(e) Calcium carbonate.
Q 45.
What is gram-molecular mass of a substance?
Q 46.
What do we call those particles which have more or less electrons than the normal atoms ?
Q 47.
What are the postulates of Dalton's atomic theory?
Q 49.
Fill in the blanks:
_________ are building block of all matter.
Q 50.
Fill in the blanks:
Atoms can be observed using ____________ Microscope.
