What is the principle behind Carbon-13 NMR spectroscopy?

• Detection of nuclear spin states of carbon-13 isotopes

• Measurement of electron spin resonance

• Observation of carbon-12 isotopes

• Analysis of molecular vibrations

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NGSS.HS-PS4-3

Which of the following is a common solvent used in Carbon NMR spectroscopy?

• Water

• Chloroform-d

• Ethanol

• Acetone

In Carbon NMR, what does the chemical shift indicate?

• The number of carbon atoms in a molecule

• The environment surrounding a carbon atom

• The molecular weight of the compound

• The temperature of the sample

What is the typical range of chemical shifts for carbon atoms in Carbon NMR?

• 0-10 ppm

• 10-220 ppm

• 220-400 ppm

• 400-600 ppm

Which isotope of carbon is primarily used in Carbon NMR spectroscopy?

• Carbon-12

• Carbon-13

• Carbon-14

• Carbon-15

What is the role of the decoupling technique in Carbon NMR?

• To enhance the signal of carbon-12

• To remove splitting caused by hydrogen atoms

• To increase the resolution of the spectrum

• To decrease the noise in the spectrum

How does the presence of electronegative atoms affect the chemical shift in Carbon NMR?

• It causes a downfield shift

• It causes an upfield shift

• It has no effect

• It broadens the signal

What is the purpose of using a reference compound like TMS in Carbon NMR?

• To calibrate the magnetic field

• To provide a zero point for chemical shifts

• To increase the sensitivity of the instrument

• To stabilize the sample

Which of the following is a limitation of Carbon NMR spectroscopy?

• It cannot detect carbon-13 isotopes

• It requires a large amount of sample

• It has low sensitivity compared to proton NMR

• It cannot be used for solid samples

What type of information can be obtained from a Carbon NMR spectrum?

• Molecular weight

• Functional groups present

• Exact molecular formula

• Melting point