Question:
Calculate the molecular masses of the following compounds :
(a) Methane, CH
Answer:
(a)16u (b) 30 u (c) 28 u (d) 26 u
Atoms and Molecules
Q 1.
Write the full form of IUPAC.
Q 2.
What is the mass of:
(a) 0.2 mole of oxygen atoms?
(b) 0.5 mole of water molecules?
Q 3.
What name is given to the number 6.022 x 10
23
Q 4.
How many moles are 3.6 g of water ?
Q 5.
How many moles of calcium carbonate (CaCO
3) are are present in 10 g of the substance ? (Ca = 40 u • C= 12 u-O = 16 u)
Q 6.
An element Z has a valency of 3. What is the formula of oxide of Z ?
Q 7.
What is the numerical value of Avogadro number ?
Q 8.
If one mole of nitrogen molecules weighs 28 g, calculate mass of one molecule of nitrogen in grams.
Q 9.
What is an ion ? How is an ion formed ? Explain with the help of two examples of different ions.
Q 10.
Calculate the molecular mass of chloroform (CHC1
3).
(Atomic masses :C= 12u;H = lu;Cl = 35.5u)
Q 11.
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 12.
What is the mass of 0.2 mole of oxygen atoms ?
Q 13.
If 16 g of oxygen contains 1 mole of oxygen atoms, calculate the mass of one atom of oxygen.
Q 14.
Is there any exception to law of conservation of mass?
Q 15.
What is relative atomic mass of an element? How it is related to atomic mass unit?
Q 16.
Fill in the blanks:
The chemical symbol of mercury is _________.
Q 17.
How many moles are there in 4.6 gms of Sodium(Na)?
Q 18.
What is meant by atomicity ? Explain with two
Q 19.
The molecular formula of glucose is C
6H12O6. Calculate its molecular mass. (Atomic masses : C = 12 u ; H =1 u ; O = 16 u)
Q 20.
What do we call those particles which are formed :
(a)by the gain of electrons by atoms ?
(b)by the loss of electrons by atoms ?
Q 21.
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 22.
Calculate the number of molecules in 4 g of oxygen.
Q 23.
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 24.
Give four examples of diatomic molecules.
Q 25.
How many atoms are present in a
(i) H
2S molecule and
(ii) PO
43- ion?
Q 26.
Who introduced the term 'mole' in chemistry?
Q 27.
Dalton's atomic theory says that atoms are indivisible. Is this statement still valid ? Give reasons for answer.
Q 28.
Calculate the molecular masses of the following :
(a) Hydrogen, H
2 (b) Oxygen O2 © Chlorine Cl2 (d) Ammonia NH3 (e) Carbon dioxide, CO2
(Atomic masses : H=1 U;O=16 U; Cl=35.5 U;N=14 U;C=12 U)
Q 29.
Work out the formulae for the following compounds :
(a) Sodium oxide
Q 30.
What name is given to the amount of substance containing 6.022 x 10
23particles (atoms, molecules or ions) ofa substance?
Q 31.
Calculate the mass in grams of 0.17 mole of hydrogen sulphide, H
2S.
Q 32.
(a) Define gram atomic mass of a substance.How much is the gram atomic mass of oxygen ?
(b) How many moles of oxygen atoms are present in one mole of the following compounds ?
(i)Al
2O3(ii) co
2(iii) C1
2O7 (iv) H
2SO4(p)A1
2(S04)3
Q 33.
If 12 g of carbon is burnt in the presence of 32 g of oxygen, how much carbon dioxide will be formed?
Q 34.
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 35.
Fill in the blanks:
The _______________ of a compound is a symbolic representation of its composition.
Q 36.
Fill in the blanks:
___________ is the combining capacity of an element.
Q 37.
Name the international organization who approves names of elements.
Q 38.
Write the chemical symbols of the following:
(i) Gold
(ii) Iron
(iii) Chlorine
(iv) Mercury
Q 39.
Can atoms of an element exist independently? Give examples of elements which exist in atomic form. Give examples of elements that do not exist in atomic form.
Q 40.
Fill in the blanks:
The atomicity of sulphur S
8 is ________.
Q 41.
Fill in the blanks:
____________ is formed by the loss of one or more electrons by an atom.
Q 42.
What is gram-molecular mass of a substance?
Q 43.
Define mole. What is its significance?
Q 44.
When 'mole' was chosen internationally standard way to express larger number of chemical units?
Q 45.
Name the unit in which the radius of an atom is usually expressed.
Q 46.
Define 'molecular mass' of a substance.
Q 47.
Calculate the molecular masses of the following compounds :
(a) Methanol, CH
3OH
(b) Ethanol, C2H5OH
Q 48.
What do we call those particles which have more or less electrons than the normal atoms ?
Q 49.
State whether the following statements are true or false :
(a)A sodium ion has positive charge because it has more protons than a neutral atom
(b)A chloride ion has negative charge because it has more electrons than a neutral atom.
Q 50.
Name the elements water is made of. What are the valencies of these elements ? Work out the chemical formula for water.