CBSE Class 12 Chemistry Important Questions for Board Exam 2024 PDF download free from the direct link given below in the page. 

CBSE Class 12 Chemistry Important Questions for Board Exam 2024

The 12th chemistry important questions are reliable and accurate references for students to understand the chapter and answer questions efficiently. The important questions for chemistry class 12 give the students an in-depth knowledge of chemistry, making their preparation for exams more effective and productive. By preparing with Chemistry Important Questions Class 12, students can become confident to answer the questions in their board exam.

CBSE Board exam for class 12 Chemistry has been scheduled for February 27, 2024. It will have different types of questions, like MCQs, assertion-based questions, short-answer type questions, long-answer type questions, and case study based questions.

Important Questions for Class 12th Chemistry with Solutions

Q.1. Many people believe that James Watson and Francis Crick discovered DNA in the 1950s. In reality, this is not the case. Rather, DNA was first identified in the late 1860s by Swiss chemist Friedrich Miescher. Then, in the decades following Miescher’s discovery, other scientists–notably, Phoebus Levene and Erwin Chargaff–carried out a series of research efforts that revealed additional details about the DNA molecule, including its primary chemical components and the ways in which they joined with one another. Without the scientific foundation provided by these pioneers, Watson and Crick may never have reached their groundbreaking conclusion of 1953: that the DNA molecule exists in the form of a three-dimensional double helix. Chargaff, an Austrian biochemist, as his first step in this DNA research, set out to see whether there were any differences in DNA among different species.

After developing a new paper chromatography method for separating and identifying small amounts of organic material, Chargaff reached two major conclusions: (i) the nucleotide composition of DNA varies among species. (ii) Almost all DNA, no matter what organism or tissue type it comes from maintains certain properties, even as its composition varies. In particular, the amount of adenine (A) is similar to the amount of thymine (T), and the amount of guanine (G) approximates the amount of cytosine (C). In other words, the total amount of purines (A + G) and the total amount of pyrimidines (C + T) are usually nearly equal. This conclusion is now known as “Chargaff’s rule.” Chargaff’s rule is not obeyed in some viruses. These either have single- stranded DNA or RNA as their genetic material. Answer the following questions: a. A segment of DNA has 100 adenine and 150 cytosine bases.

  1. What is the total number of nucleotides present in this segment of DNA? . 

Ans. A = 100 so T = 100

C=150 so  G = 150

Total nucleotides = 100+100+150+150 =500

  1. A sample of hair and blood was found at two sites. Scientists claim that the samples belong to the same species. How did the scientists arrive at this conclusion?

Ans. They studied the nucleotide composition of DNA. It was the same so they concluded that the samples belong to the same species.

  1. The sample of a virus was tested and it was found to contain 20% adenine, 20% thymine, 20 % guanine and the rest cytosine. Is the genetic material of this virus (a) DNA- double helix (b) DNA-single helix (c) RNA? What do you infer from this data?

Ans.  A = T = 20%

But G is not equal to C so double helix is ruled out.

The bases pairs are ATGC and not AUGC so it is not RNA.

The virus is a single helix DNA virus.

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