Question:
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?
Answer:
The given reaction is
Carbon + Oxygen ➜ Carbon Dioxide
3g + 8g = 11g
⇒ Total mass of reactants = Total mass of products
∴ Law of conservation of mass is obeyed.
It also shows that carbon dioxide (CO
2) contains carbon and oxygen in fixed ratio i.e. 3:8 which follows Law of Constant proportion.
⇒ 3g of carbon (C) will react with 8g of oxygen (O) to give 11g of carbon dioxide (CO
2).
⇒ Remaining oxygen (50 -8 = 42g) will not participate in the reaction.
Atoms and Molecules
Q 1.
What is gram-atomic mass of an element?
Q 2.
Fill in the blanks:
The atomic mass of sodium is 23. The gram atomic mass of sodium is _________.
Q 3.
What is the mass of 5 moles of sodium carbonate (Na
) ?(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Q 4.
Fill in the blanks:
According to law of definite proportions, in a chemical substance the elements are always present in __________ proportions by mass.
Q 5.
Define 'formula mass' of a compound.
Q 6.
(i) State the law of constant proportions.
(ii) Show that water illustrates the law of constant proportions.
Q 7.
Give four examples of diatomic molecules.
Q 8.
Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Q 9.
If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
Q 10.
What are the postulates of Dalton's atomic theory?
Q 11.
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 12.
What is the chemical symbol for iron?
Q 13.
How many atoms are there in 0.25 mole of hydrogen ?
Q 14.
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 15.
(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
(ii) co
2(iii) C1
(iv) H
(p)A1
Q 16.
Fill in the blanks:
The mass of 1 mole of a substance is called its _____________.
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.
What are polyatomic ions? Give examples?
Q 19.
What are ionic compounds?
Q 20.
Define mole. What is its significance?
Q 21.
Who introduced the term 'mole' in chemistry?
Q 22.
What are the building blocks of matter ?
Q 23.
What is meant by atomicity ? Explain with two
Q 24.
Calculate the molecular mass of nitric acid,HNO
Q 25.
Calculate the molecular mass of hydrogen bromide (HBr).
(Atomic masses: H=1; Br= 80 U)
Q 26.
Name the following compounds. Also write the symbols/formulae of the ions present in them :
(a) CuSO
Q 27.
What is an ion ? How is an ion formed ? Explain with the help of two examples of different ions.
Q 28.
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 29.
Fill in the following blanks :
(a)1 mole Contains...........atoms- molecules or ions of a substance
(b)A mole represents an..........number of Particles of a substance.
(c)60 g of carbon element are...........moles of carbon atoms.
(d) 0.5 mole of calcium element has a mass of..........
(e) 64 g of oxygen gas contains..........moles of oxygen atoms.
Q 30.
If one mole of nitrogen molecules weighs 28 g, calculate mass of one molecule of nitrogen in grams.
Q 31.
Calculate the number of molecules in 4 g of oxygen.
Q 32.
Calculate the mass in grams of 0.17 mole of hydrogen sulphide, H
Q 33.
What is the law of conservation of mass?
Q 34.
Who proposed Law of Definite Proportions (or Law of Constant Composition)?
Q 35.
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 36.
Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?
Q 37.
Fill in the blanks:
Atomic radius is measured in __________.
Q 38.
Fill in the blanks:
_________ are building block of all matter.
Q 39.
Name the international organization who approves names of elements.
Q 40.
What is the significance of a chemical symbol?
Q 41.
What is relative atomic mass of an element? How it is related to atomic mass unit?
Q 42.
Fill in the blanks:
According to Dalton's atomic theory, atoms of different elements differ in ______, size and chemical properties.
Q 44.
(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 45.
Give examples of triatomic molecules.
Q 46.
Write down the formulae of
(i) sodium oxide
(ii) aluminium chloride
(iii) sodium suphide
(iv) magnesium hydroxide
Q 47.
What is the molecular mass of a substance?
Q 48.
What is Formula Unit Mass? How it is different from molecular mass?
Q 49.
How do we know the presence of atoms if they do not exist independently for most of the elements?
Q 50.
What is molar mass?
