Atomic and Molecular Mass

How many moles of lead (II) chloride will be formed from a reaction between 6.5 g of  $\text{PbO}$ and 3.2 g of  $\mathrm{HCl}$? Molar mass of $\mathrm{PbO}$ is equal to 223 g/mol.

20% of surface sites are occupied by ${\mathrm{N}}_2$ molecules. The density of surface sites is $6.023\times {10}^{14}{\mathrm{cm}}^{-2}$ and total surface area is $1000 {\mathrm{cm}}^2$. The catalyst is heated to 300 K while ${\mathrm{N}}_2$ is completely desorbed into a pressure of 0.001 atm and volume of $2.46 {\mathrm{cm}}^3$. The number of active sites occupied by each ${\mathrm{N}}_2$ molecule will be:

A mixture of ${\mathrm{O}}_2$ and gas $\mathrm{Y}$ (mol. wt. 80) in the mole ratio $\mathrm{a}:\mathrm{b}$ has a mean molecular weight 40. What would be mean molecular weight, if the gases are mixed in the ratio $\mathrm{b}:\mathrm{a}$ under identical conditions? (Gases are non-reacting)

Specific heat of a metal is $0.031\frac{{}^{\circ }\mathrm{C}\times \mathrm{Cal}}{\mathrm{g}}$, and its equivalent weight is $103.6$. Calculate the exact atomic weight of the metal.

Round off your answer up to one decimal place.

Which atom was originally used as a reference element for defining the atomic masses of other atoms.

Many elements have nonintegral atomic masses because-

Oxygen as a reference element was rejected because oxygen has other isotopes as well.

The relative atomic mass of nitrogen assuming oxygen as the reference element is

Define amu assuming oxygen as the reference element.

Calculate the atomic mass of nitrogen assuming oxygen as the reference element.

In the nineteenth century, scientists could determine mass of one atom relative to another by experimental methods using Avogadro's hypothesis. Earlier, hydrogen was used as the reference element being the lightest atom, but the present system of atomic masses is based on carbon-$12$ as the standard and has been agreed upon in the year _____.

In the nineteenth century, scientists used to determine the absolute mass of an atom using technique called mass spectrometry.

Discuss the need of reference element in the calculation of atomic masses.

Which element is used as a reference element in the present system of atomic masses?

What is the difference between mass number and relative atomic mass?

Carbon- _____ is the reference for all atomic mass calculations. ($10/11/12$)

Is hydrogen the standard for atomic mass?

A gas mixture contains $50\raisebox{1ex}{$ o$}\!\left/ \!\raisebox{-1ex}{$o$}\right.$ helium and $50 \raisebox{1ex}{$o$}\!\left/ \!\raisebox{-1ex}{$o$}\right.$ methane by volume. What is the percentage by weight of methane in the mixture?

The charge on $1$ $\mathrm{gram}$ ions of ${\mathrm{Al}}^{3+}$ is: $\left({\mathrm{N}}_{\mathrm{A}}=\right.$Avogadro number, $\mathrm{e}=$ charge of one electron$)$