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:
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.
Name the international organization who approves names of elements.
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.
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 10.
What is the mass of 5 moles of sodium carbonate (Na
) ?(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Q 11.
Give four examples of diatomic molecules.
Q 13.
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 14.
(i) State the law of constant proportions.
(ii) Show that water illustrates the law of constant proportions.
Q 15.
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 16.
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 17.
Fill in the blanks:
According to law of definite proportions, in a chemical substance the elements are always present in __________ proportions by mass.
Q 18.
What are polyatomic ions? Give examples?
Q 19.
How many atoms are there in 0.25 mole of hydrogen ?
Q 20.
Name the element having following Latin names
(i) Stibium
(ii) Cuprum
(iii) Argentum
(iv) Natrium
(v) Stannum
(vi) Wolfram
(vii) plumbum
(viii) Kalium
Q 21.
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 22.
Fill in the blanks:
The chemical symbol of mercury is _________.
Q 23.
Convert 12 g of oxygen gas into moles.
Q 24.
Who established the two important laws of chemical combinations?
Q 25.
Fill in the blanks:
The mass of 5 moles of ammonia (NH
3) is __________.
Q 26.
Based on type of substance, how molecules are classified?
Q 27.
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 28.
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 29.
State Law of constant proportions. Explain with an example.
Q 30.
Fill in the blanks:
The mass of 1 mole of a substance is called its _____________.
Q 31.
Fill in the blanks:
_________ are building block of all matter.
Q 32.
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 33.
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 34.
How will you define chemical symbol?
Q 35.
Fill in the blanks:
An element has only one type of __________.
Q 36.
Fill in the blanks:
Hydrogen and oxygen combines to form H
2O and H
2O
2. These two compounds obey the law of ____________________.
Q 38.
(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 39.
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 40.
How many moles are there in 4.6 gms of Sodium(Na)?
Q 41.
If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
Q 42.
Calculate the number of molecules of phosphorus (P
4) present in 31 gram of phosphorus.
Q 43.
Dalton's atomic theory says that atoms are indivisible. Is this statement still valid ? Give reasons for answer.
Q 44.
An element Z has a valency of 3. What is the formula of oxide of Z ?
Q 45.
What are the postulates of Dalton's atomic theory?
Q 46.
Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
Q 47.
What is the significance of a chemical symbol?
Q 48.
Which element has the smallest atom in size?
Q 49.
What is relative atomic mass of an element? How it is related to atomic mass unit?
Q 50.
Fill in the blanks:
The chemical symbol of flourine is ________.
