Question:
Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Answer:
(a) Quick lime: Calcium Oxide (CaO), Elements Present: Calcium(Ca), Oxygen(O)
(b) Hydrogen bromide: HBr, Elements Present: Hydrogen (H), Bromine(Br)
(c) Baking powder: Sodium Bicarbonate (NaHCO3) Elements Present: Sodium(Na), Hydrogen(H), Carbon(C) and Oxygen(O).
(d) Potassium sulphate: K2SO4Elements Present:Potassium(K), Sulphur(S), Oxygen(O)
Atoms and Molecules
Q 1.
Fill in the blanks:
According to law of definite proportions, in a chemical substance the elements are always present in __________ proportions by mass.
Q 2.
What is gram-atomic mass of an element?
Q 3.
Define 'formula mass' of a compound.
Q 4.
Fill in the blanks:
The atomic mass of sodium is 23. The gram atomic mass of sodium is _________.
Q 5.
What is the mass of 5 moles of sodium carbonate (Na
) ?(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Q 6.
What is the chemical symbol for iron?
Q 7.
Define molecule. What are its important properties?
Q 8.
Give four examples of diatomic molecules.
Q 9.
Write the chemical symbols of the following:
(i) Gold
(ii) Iron
(iii) Chlorine
(iv) Mercury
Q 10.
How many atoms are there in 0.25 mole of hydrogen ?
Q 11.
Who proposed Law of Definite Proportions (or Law of Constant Composition)?
Q 12.
Dalton's atomic theory says that atoms are indivisible. Is this statement still valid ? Give reasons for answer.
Q 13.
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 14.
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 15.
What are the postulates of Dalton's atomic theory?
Q 16.
Fill in the blanks:
Atomic radius is measured in __________.
Q 17.
Name the element having following Latin names
(i) Stibium
(ii) Cuprum
(iii) Argentum
(iv) Natrium
(v) Stannum
(vi) Wolfram
(vii) plumbum
(viii) Kalium
Q 18.
If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
Q 19.
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 20.
Magnesium and oxygen combine in the ratio of 3 : 2 by mass to form magnesium oxide. How much oxygen is required to react completely with 12 g of magnesium?
Q 21.
Name one element each which forms diatomic and tetra atomic molecule.
Q 22.
What is the numerical value of Avogadro number ?
Q 23.
Calculate the mass in grams of 0.17 mole of hydrogen sulphide, H
Q 24.
Explain with example that law of conservation of mass is valid for chemical reactions.
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.
Fill in the blanks:
_________ are building block of all matter.
Q 27.
Fill in the blanks:
Atoms can be observed using ____________ Microscope.
Q 29.
What are polyatomic ions? Give examples?
Q 30.
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 31.
Who established the two important laws of chemical combinations?
Q 32.
State Law of constant proportions. Explain with an example.
Q 33.
A 0.24 g sample of compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound by weight.
Q 34.
Name the international organization who approves names of elements.
Q 35.
Which element has the smallest atom in size?
Q 36.
Fill in the blanks:
The chemical symbol of flourine is ________.
Q 37.
Fill in the blanks:
The chemical symbol of mercury is _________.
Q 38.
Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Q 39.
What are ionic compounds?
Q 40.
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 41.
Calculate the molecular mass of chloroform (CHC1
Q 42.
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 43.
Why do atoms of the most of the elements not exist independently?
Q 44.
What is relative atomic mass of an element? How it is related to atomic mass unit?
Q 45.
Write down the formulae of
(i) sodium oxide
(ii) aluminium chloride
(iii) sodium suphide
(iv) magnesium hydroxide
Q 46.
What is Formula Unit Mass? How it is different from molecular mass?
Q 47.
Name one element which forms diatomic and triatomic molecule.
Q 48.
What is molar mass?
Q 49.
Who introduced the term 'mole' in chemistry?
Q 50.
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)?
