CBSE 11TH CHEMISTRY - Online Test
Q1. Choose the most appropriate answer amongst the options given below for the statement -
" A solution of a desired concentration is prepared by diluting --------------- ."
Answer : Option D
Explaination / Solution:
Stock solution can best be described as concentrated solution of known accurate concentration that will be used for future laboratory use.
Since large amounts of solutes are used for preparing stock solution a more accurate concentration of it can be achieved quite easily, and as such the chances are slim to get erroneous results of the related experiments..
In addition , stock solutions are generally more stable as compared to working solution since they usually do not suppport bacterial growth.
A multiple working solution can be prepaed by dilution of stock solution using easy calculation and process.
Q2. In the gas phase water is a bent molecule with a bond angle of
Answer : Option B
Explaination / Solution:
Because the two non-bonding pairs remain closer to the oxygen atom, these exert a stronger repulsion against the two covalent bonding pairs, effectively pushing the two hydrogen atoms closer together. The result is a distorted tetrahedral arrangement in which the H—O—H angle is 104.5°
Q3. The shift in electron density is symbolised by crossed arrow in the below diagram. It depicts
Answer : Option B
Explaination / Solution:
The cross base arrow demonstrates the net dipole. On the cross-base arrow, the cross represents the positive charge and the arrow represents the negative charge.
Q4. Carius tube is used in the estimations of one of the following
Answer : Option C
Explaination / Solution:
It is used in the estimation of Halogen and Sulphur.
Q5. The alkali metals dissolve in liquid ammonia giving deep blue solutions. When they become diamagnetic, the solution turns into
Answer : Option C
Explaination / Solution:
When the solution become diamagnetic due to formation of electron cluster in which ammoniated electron with opposite spin group- it changes its color to bronze.
Q6. The three states of matter of are in equilibrium at
Answer : Option A
Explaination / Solution:
Triple point is the point where all the three states coexist in equilibrium.
Q7. Hydronium ion concentration in molarity is more conveniently expressed on a logarithmic scale known as the
Answer : Option A
Explaination / Solution:
pH= -log[]
Q8. Aromatic compounds are charachterized by the presence of _____ π electrons in the ring where n is an integer (n = 0, 1, 2, . . .).
Answer : Option D
Explaination / Solution:
Huckel rule which explains the unusual stability of cyclic conjugated polyenes(i.e. aromatic compounds) over other cyclic unsaturatrd compounds which do not contain (4n+2) pi electrons.
Q9. Oxidation number of −1/2 is assigned to oxygen atom in
Answer : Option B
Explaination / Solution:
In the superoxide ion, O2−, the oxygen has an oxidation number of −1/2. The stability of metal superoxides depends on the size and the electropositive character of the metal. The larger the metal and the more electropositive it is, the greater the stability of its superoxide.
Q10. If change in Gibbs energy ΔG is negative (< 0) at constant pressure and temperature
Answer : Option B
Explaination / Solution:
ΔG gives a criteria for spontaneous and non spontaneous process at constant temperature and pressure. ΔG < 0 (negative) means reaction is spontaneous and ΔG >0 (positive) means reaction is non spontanenous.
