CBSE Class 12 Chemistry Marking Scheme 2020 along with the latest CBSE 12th Chemistry Sample Paper 2020 is available here for download in PDF format. Students of CBSE Schools having Chemistry as one of their subjects can download these resources from the download link given at the end of this article.
Latest CBSE Class 12 Chemistry Marking Scheme 2020 is explained with the help of CBSE Class 12 Chemistry Sample Paper. The Sample Paper contains questions as per the latest exam pattern of Class 12 Chemistry Board exam whereas the Marking Scheme contains answers (or hints) of these questions and step-wise marking scheme.
Also Read: CBSE Class 12 Date Sheet 2020
Content from CBSE Class 12 Chemistry Marking Scheme & Sample Paper:
Here we have published some content from CBSE Class 12 Chemistry Marking Scheme & Sample Paper so that students can get a clear idea about both the resources.
SECTION - A
Read the given passage and answer the questions 1 to 5 that follow:
A Lead storage battery is the most important type of secondary cell having a lead anode and a
grid of lead packed with PbO2 as cathode. A 38% solution of sulphuric acid is used as electrolyte. (Density=1.294 g mL-1) The battery holds 3.5 L of the acid. During the discharge of the battery, the density of H2SO4 falls to 1.139 g mL-1. (20% H2SO4 by mass)
(1) Write the reaction taking place at the cathode when the battery is in use.
Answer1: Reaction taking place at cathode when the battery is in use:
PbO2(s) + SO42- (aq) + 4H+ (aq) + 2e- → PbSO4 (s) + 2H2O (l)
(2) How much electricity in terms of Faraday is required to carry out the reduction of one mole of PbO2?
(3) What is the molarity of sulphuric acid before discharge?
Molarity = [(38 x 1.294 x 1000)/(98 x 100)] = 5.02 M
(4) Lead storage battery is considered a secondary cell. Why?
Answer4: It can be recharged after use.
(5) Write the products of electrolysis when dilute sulphuric acid is electrolysed using Platinum electrodes.
At anode: O2 (g)
At cathode: H2 (g)
For all the questions and answers, download CBSE Class 12 Chemistry Marking Scheme & Sample Paper in PDF format.