Question:
An element Z has a valency of 3. What is the formula of oxide of Z ?
Atoms and Molecules
Q 1.
What is gram-atomic mass of an element?
Q 2.
Fill in the blanks:
According to law of definite proportions, in a chemical substance the elements are always present in __________ proportions by mass.
Q 3.
Fill in the blanks:
The atomic mass of sodium is 23. The gram atomic mass of sodium is _________.
Q 4.
How many atoms are there in 0.25 mole of hydrogen ?
Q 5.
Define 'formula mass' of a compound.
Q 6.
What is the chemical symbol for iron?
Q 7.
What is the mass of 5 moles of sodium carbonate (Na
) ?(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Q 8.
Who established the two important laws of chemical combinations?
Q 9.
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 10.
Write the chemical symbols of the following:
(i) Gold
(ii) Iron
(iii) Chlorine
(iv) Mercury
Q 11.
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 12.
Name one element each which forms diatomic and tetra atomic molecule.
Q 13.
Who proposed Law of Definite Proportions (or Law of Constant Composition)?
Q 14.
Name the international organization who approves names of elements.
Q 15.
Define molecule. What are its important properties?
Q 16.
If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
Q 17.
What are the postulates of Dalton's atomic theory?
Q 18.
What is the significance of a chemical symbol?
Q 19.
Fill in the blanks:
The chemical symbol of flourine is ________.
Q 20.
Give four examples of diatomic molecules.
Q 22.
State Law of constant proportions. Explain with an example.
Q 23.
Name the element having following Latin names
(i) Stibium
(ii) Cuprum
(iii) Argentum
(iv) Natrium
(v) Stannum
(vi) Wolfram
(vii) plumbum
(viii) Kalium
Q 24.
Fill in the blanks:
The chemical symbol of mercury is _________.
Q 25.
What are ionic compounds?
Q 26.
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 27.
When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen? Which law of chemical combination will govern your answer?
Q 28.
Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
Q 29.
Fill in the blanks:
Atomic radius is measured in __________.
Q 30.
Fill in the blanks:
Atoms can be observed using ____________ Microscope.
Q 31.
What is relative atomic mass of an element? How it is related to atomic mass unit?
Q 32.
What are polyatomic ions? Give examples?
Q 33.
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 34.
Which element has the smallest atom in size?
Q 35.
Give examples of triatomic molecules.
Q 36.
Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Q 37.
How many atoms are present in a
(i) H
2S molecule and
(ii) PO
43- ion?
Q 38.
What is the molecular mass of a substance?
Q 39.
How do we know the presence of atoms if they do not exist independently for most of the elements?
Q 40.
Define mole. What is its significance?
Q 41.
What are the building blocks of matter ?
Q 42.
Give one major drawback of Dalton's atomic theory of matter.
Q 43.
Calculate the molecular mass of ethanoic acid, CH
Q 44.
Calculate the molecular mass of chloroform (CHC1
Q 45.
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 46.
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 47.
What is the numerical value of Avogadro number ?
Q 48.
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 49.
(a) What is meant by 'a mole of carbon atoms' ?
(b)(b) Which has more atoms, 50 g of aluminium or 50 g of iron ? Illustrate your answer with the help of calculations.
(Atomic masses : A1 = 27 u ; Fe = 56 u)
Q 50.
Give an example to show Law of conservation of mass applies to physical change also.
