Question:
Calculate the mole ratio of 240 g of calcium and 240 g of magnesium. (Ca = 40 u ; Mg = 24 u)
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.
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.
What is gram-atomic mass of an element?
Q 4.
What is the mass of 5 moles of sodium carbonate (Na
) ?(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Q 5.
Define 'formula mass' of a compound.
Q 6.
If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
Q 7.
What are the postulates of Dalton's atomic theory?
Q 8.
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 9.
Give four examples of diatomic molecules.
Q 10.
What are polyatomic ions? Give examples?
Q 11.
Dalton's atomic theory says that atoms are indivisible. Is this statement still valid ? Give reasons for answer.
Q 12.
Who proposed Law of Definite Proportions (or Law of Constant Composition)?
Q 13.
Fill in the blanks:
Atomic radius is measured in __________.
Q 14.
How many atoms are there in 0.25 mole of hydrogen ?
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.
Fill in the blanks:
The mass of 1 mole of a substance is called its _____________.
Q 17.
Write the chemical symbols of the following:
(i) Gold
(ii) Iron
(iii) Chlorine
(iv) Mercury
Q 18.
Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Q 19.
What is the chemical symbol for iron?
Q 20.
What is relative atomic mass of an element? How it is related to atomic mass unit?
Q 21.
Fill in the blanks:
According to Dalton's atomic theory, atoms of different elements differ in ______, size and chemical properties.
Q 23.
What are ionic compounds?
Q 24.
What are the building blocks of matter ?
Q 25.
What is meant by atomicity ? Explain with two
Q 26.
Calculate the mass in grams of 0.17 mole of hydrogen sulphide, H
Q 27.
(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 28.
Write down the formulae of
(i) sodium oxide
(ii) aluminium chloride
(iii) sodium suphide
(iv) magnesium hydroxide
Q 29.
Define mole. What is its significance?
Q 30.
Find out number of atoms in 15 moles of He.
Q 31.
'If 100 grams of calcium carbonate (whether in the form of marble or chalk) are decomposed completely,then 56 grams of calcium oxide and 44 grams of carbon dioxide are obtained'.Which law of chemical combination is illustrated by this statement ?
Q 32.
Calculate the molecular masses of the following compounds :
(a) Methanol, CH
Q 33.
How many moles are there in 34.5 g of sodium ? (Atomic mass of Na = 23 u)
Q 34.
Calculate the number of molecules in 4 g of oxygen.
Q 35.
What is the law of conservation of mass?
Q 36.
Fill in the blanks:
Atoms can be observed using ____________ Microscope.
Q 37.
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 38.
Fill in the blanks:
The chemical symbol of flourine is ________.
Q 39.
How many moles are there in 4.6 gms of Sodium(Na)?
Q 40.
What is meant by the symbol of an element ? Explain with examples.
Q 41.
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 42.
Write down the formulae for the following compounds :
(a) Calcium oxide
(b) Magnesium hydroxide
Q 43.
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 44.
What are (ionic compounds, and (ii) molecular compounds ? Give two examples of each type of compounds.
Q 45.
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 46.
What name is given to the amount of substance containing 6.022 x 10
Q 47.
Calculate the mole ratio of 240 g of calcium and 240 g of magnesium. (Ca = 40 u ; Mg = 24 u)
Q 48.
(a) What is meant by the 'molar mass'of a substance ? State the unit in which molar mass usually expressed.
(b) Calulate the molar masses of the following substances. Write the results with proper units
(1) Ozone molecule, O
Q 49.
State Law of constant proportions. Explain with an example.
Q 50.
(i) State the law of constant proportions.
(ii) Show that water illustrates the law of constant proportions.
