# Category Exceptional Publications

## Calculate the percentage of nitrogen in NH2CONH2.

ANSWER: Molar mass of urea = 14+2+12+16+14+2 = 60 g Mass of N in the molecule = 28 g % of N = Mass of N / Molar Mass ✕ 100 = 28 gmol-1 / 60 gmol-1 ✕ 100 =…

## Differentiate between qualitative and quantitative analyses.

ANSWER: QUALITATIVE ANALYSIS In qualitative analysis, the elements present in a compound are identified. QUANTITATIVE ANALYSIS In quantitative analysis, the relative amount of each element in a compound is determined. (Ref. An Insight Into Objective Chemsitry-11, Ch-01, Q. No. 29)

## What is the justification of two equally strong peaks in the mass spectrum for bromine, while for iodine only one peak at 127amu is indicated?

ANSWER: In mass spectrum, the number of peaks tells about the number of isotopes, while the heights of the peaks represent their natural abundance. Two equally strong peaks in the mass spectrum of bromine indicate that bromine has two isotopes…

## No individual Neon atom in the sample of the element has a mass of 20.18 amu. Explain.

ANSWER: Neon has three isotopes Ne–20, Ne–21 & Ne–22, having percentage abundance of 90.92%, 0.26% & 8.82% respectively. When we calculate average of all these isotopic masses in proportion to their natural abundances, a fractional value of 20.18 amu is…

## Why do most of the elements have fractional atomic masses?

ANSWER: Most of the elements have fractional atomic masses. This is because most elements have isotopes, each with different natural abundance. The atomic mass is actually the average of all the isotopic masses, proportional to their relative abundance. So, their…

## Write down any four methods used for the separation of isotopes.

ANSWER: Methods for the Separation of Isotopes: Isotopes have different physical properties, so they can be separated by the methods based on these properties. Some of these methods are: 1) Gaseous diffusion 2) Thermal diffusion 3) Electromagnetic separation 4) Laser…

## What is electrometer? Give its function in mass spectrometer.

ANSWER: Function of Electrometer: The electrometer collects the positive ions and develops the electric current. The strength of the current gives the relative abundance of the isotope. (Ref. An Insight Into Objective Chemsitry-11, Ch-01, Q. No. 25)

## What is the function of magnetic field in mass spectrometer?

ANSWER: Function of Magnetic Field: When an accelerated beam of isotopic positive ions is allowed to pass through a strong magnetic field, the field makes them move in a circular path. The ions are, thus, separated on the basis of…

## What is the function of ionization chamber in mass spectrometer?

ANSWER: Function of Ionization Chamber: In ionization chamber, fast moving electrons are thrown upon the vapours of the substance. The atoms of the isotopic element are converted into positively charged ions. (Ref. An Insight Into Objective Chemsitry-11, Ch-01, Q. No.…

## Draw a labelled diagram of Dempster’s mass spectrometer.

ANSWER: Dempster’s Mass Spectrometer: (Ref. An Insight Into Objective Chemsitry-11, Ch-01, Q. No. 22)