List of top Chemistry Questions asked in CBSE Class XI

Which element do you think would have been named by
(i) Lawrence Berkeley Laboratory
(ii) Seaborg's group?
Write the atomic number of the element present in the third period and seventeenth group of the periodic table.
In terms of period and group where would you locate the element with Z =114?
On the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 elements.
What is the basic difference in approach between the Mendeleev's Periodic Law and the Modern Periodic Law?
Which important property did Mendeleev use to classify the elements in his periodic table and did he stick to that? 
What is the basic theme of organisation in the periodic table?
How many significant figures are present in the following? 
(i) 0.0025 
(ii) 208 
(iii) 5005 
(iv) 126,000 
(v) 500.0 
(vi) 2.0034
Round up the following upto three significant figures: 
(i) 34.216 
(ii) 10.4107 
(iii) 0.04597 
(iv) 2808
Express the following in the scientific notation: 
(i) 0.0048 
(ii) 234,000 
(iii) 8008 
(iv) 500.0 
(v) 6.0012
What do you mean by significant figures?
What is the SI unit of mass? How is it defined?
Pressure is determined as force per unit area of the surface. The SI unit of pressure, pascal is as shown below:
\(1\text{Pa} = 1\text{N m}^{–2} \)
If mass of air at sea level is \(1034\, \text{g cm}^{–2}\), calculate the pressure in pascal.
If the density of methanol is \(0.793\, \text{kg L}^{–1}\), what is its volume needed for making 2.5 L of its 0.25 M solution?
In three moles of ethane \((\text{C}_2\text{H}_6)\), calculate the following: 
(i) Number of moles of carbon atoms. 
(ii) Number of moles of hydrogen atoms. 
(iii) Number of molecules of ethane.
Calculate the atomic mass (average) of chlorine using the following data: 
                                                   % Natural Abundance                                Molar Mass 
\(^{35}\text{Cl}\)                                                         75.77                                                34.9689 
\(^{37}\text{Cl}\)                                                         24.23                                                36.9659
How much copper can be obtained from 100 g of copper sulphate \((\text{CuSO}_4)\)?
Calculate the mass of sodium acetate \((\text{CH}_3\text{COONa})\) required to make 500 mL of 0.375 molar aqueous solution. Molar mass of sodium acetate is \(82.0245\, \text{g mol}^{–1}.\)
Calculate the mass per cent of different elements present in sodium sulphate \((\text{Na}_2\text{SO}_4)\).
Calculate the molar mass of the following: 
(i) \(\text{H}_2\text{O}\) (ii) \(\text{CO}_2\) (iii) \(\text{CH}_4\)