CBSE 11TH CHEMISTRY - Online Test
Q1. The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following rules is not correct in this respect?
Answer : Option C
Explaination / Solution:
as oxygen is more electronegative than Cl,Br and I. So they have positive oxidation state.
Q2. The molarity of NaOH in a solution prepared by dissolving its 4.0 g in enough water to form 250 mL of the solution is ,
Answer : Option C
Explaination / Solution:
Since , Molarity
=
substituting the given values , we get -
Molarity ( M )
=
=0.4M
* moles of solute ie. NaOH = mole
.= 0.1mol
Q3. Identify B and D in the following sequence of reactions.
Answer : Option C
Explaination / Solution:
Ethanolis formed on addition of water, alcoholic KOH results in formation of alkene.
Q4. The correct increasing order of atomic radii for the same element is ----?
Answer : Option D
Explaination / Solution:
For the same element ,
- Metallic radius of atoms are always greater than corresponding covalent radius.
- Metallic radius is always lesser than van der Waal's radius
Hence , the correct increasing order of atomic radii of an element is
Q5. One of the orbitals is non-directional
Answer : Option D
Explaination / Solution:
Orbitals with subshell quantum number l = 0 are called s orbitals. All s orbitals are spherical in shape and have spherical symmetry. This means that the wave function will depend only on the distance from the nucleus and not on the direction.
Q6. The greenhouse effect is where:
Answer : Option D
Explaination / Solution:
The greenhouse effect is where heat energy is trapped by the atmosphere
Q7. Which of the following hydrides is electron-precise hydride?
Answer : Option C
Explaination / Solution:
Electron precise hydride is the type of hydride in which the number of electrons present is equal to the number of electron required (octet or duplet). For example- CH4
CH4 has no lone pair of electron or vacant orbital so it is an electron precise hydride.
Q8. Given = –-92.4 kJ What is the standard enthalpy of formation of gas?
Answer : Option B
Explaination / Solution:
Standard Enthalpy of formation of NH3 is the energy change that take place when 1 mole of NH3 is formed from elements in standard state. For 2 moles of ammonia formation energy= –-92.4 kJ . For 1 mole energy =0.5 x–-92.4 kJ = -46.2 kJ
Q9. Which one of the following is paramagnetic?
Answer : Option C
Explaination / Solution:
The number of electrons in Nitrogen are 7 and in oxygen are 8. Hence the number of electrons that would be present in the molecular orbitals in NO are 7 + 8 = 15. As the number of electrons are odd, all the electrons in NO molecule cannot be paired. Hence, a single electron would be present in a π*2p orbital. Therefore NO is an odd electron species and the gas is hence paramagnetic due to the presence of unpaired electron.
Q10. Choose the correct order of increase in ionic size of alkaline earth metals in the options given below
Answer : Option D
Explaination / Solution:
As we move down the group ionic radii increases.
