Question:
What is the chemical symbol for iron?
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 the chemical symbol for iron?
Q 3.
What is gram-atomic mass of an element?
Q 4.
Define molecule. What are its important properties?
Q 5.
Define 'formula mass' of a compound.
Q 6.
Name the international organization who approves names of elements.
Q 7.
Name one element each which forms diatomic and tetra atomic molecule.
Q 8.
Calculate the number of molecules of phosphorus (P
4) present in 31 gram of phosphorus.
Q 9.
(i) State the law of constant proportions.
(ii) Show that water illustrates the law of constant proportions.
Q 10.
Write the chemical symbols of the following:
(i) Gold
(ii) Iron
(iii) Chlorine
(iv) Mercury
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 chemical symbol of mercury is _________.
Q 13.
What are ionic compounds?
Q 14.
What is the mass of 5 moles of sodium carbonate (Na
) ?(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Q 15.
Fill in the blanks:
The mass of 5 moles of ammonia (NH
3) is __________.
Q 16.
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 17.
Convert 12 g of oxygen gas into moles.
Q 18.
How many atoms are there in 0.25 mole of hydrogen ?
Q 19.
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 20.
Fill in the blanks:
According to law of definite proportions, in a chemical substance the elements are always present in __________ proportions by mass.
Q 21.
Give four examples of diatomic molecules.
Q 22.
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 23.
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 24.
Who established the two important laws of chemical combinations?
Q 25.
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 26.
What are polyatomic ions? Give examples?
Q 27.
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 28.
Write down the formulae for the following compounds :
(a) Calcium oxide
(b) Magnesium hydroxide
Q 29.
Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
Q 30.
Based on type of substance, how molecules are classified?
Q 32.
(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 34.
Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Q 35.
Explain with example that law of conservation of mass is valid for chemical reactions.
Q 36.
State Law of constant proportions. Explain with an example.
Q 37.
What are the postulates of Dalton's atomic theory?
Q 38.
Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?
Q 39.
Fill in the blanks:
Atomic radius is measured in __________.
Q 40.
Fill in the blanks:
Atoms can be observed using ____________ Microscope.
Q 41.
Fill in the blanks:
The chemical symbol of flourine is ________.
Q 42.
Name one element which forms diatomic and triatomic molecule.
Q 43.
If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
Q 44.
What is the mass of:
(a) 0.2 mole of oxygen atoms?
(b) 0.5 mole of water molecules?
Q 45.
Fill in the blanks:
Mass of 2 Hydrogen atoms is __________.
Q 46.
Fill in the blanks:
The mass of 1 mole of a substance is called its _____________.
Q 47.
What is the significance of a chemical symbol?
Q 48.
Which element has the smallest atom in size?
Q 49.
Fill in the blanks:
The atomicity of sulphur S
8 is ________.
Q 50.
How many atoms are present in a
(i) H
2S molecule and
(ii) PO
43- ion?
