Q1 State law of conservation of mass.
Q4 Define atomic mass unit.
Q5 What are molecules?
Q6 What do you mean by molecular mass?
Q7 Write the relationship between number of moles and atomic mass.
Q8 Why are chemical reactions according to law of conservation of mass?
Q9 What is basic difference between atoms and molecules?
Q10 The atomic mass of an element is in fraction .What does it mean?
Q11 What is the difference between the mass of molecule and molecular mass?
Q12 Where do we use the words mole and mol?
Q13 How many moles are present in 11.5 g of sodium?
Q14 Explain why the number of atoms in one mole of hydrogen gas is double the number of atoms in one mole of helium gas?
Q15An element Z forms an oxide with formula Z2O3. What is its valency?
Q16 The valency of an element A is 4 . Write the formula of its oxide.
Q17 An element X has valency 3 while the element Y has valency 2.Write the formula of the compound between XandY .
Q18 What are ions?
Q19 Which postulate of Dalton’s Atomic theory is the basis of law of conservation of mass?
Q20 Write the formulae of sodium oxide and aluminium chloride
Q21 Find out the ratio by mass of the combining elements in the following compounds
Q22 Define atomicity of the molecule.
Q23 What is the atomicity of oxygen,ozone,neon and sulphur?
Q24 What is wrong with the statement '1 mol of hydrogen'
Q25 The atomic mass of an element is in fraction. What does it mean?
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