Classes
Class 9Class 10First YearSecond Year
$\mathrm{NH}_{3} gas can be prepared by heating together two solids \mathrm{NH}_{4} \mathrm{Cl} and \mathrm{Ca}(\mathrm{OH})_{2} . If a mixture containing 100 \mathrm{~g} of each solid is heated then(a) Calculate the number of grams of \mathrm{NH}_{3} produced.(b) Calculate the excess amount of reagent left unreacted. 2 \mathrm{NH}_{4} \mathrm{Cl}(\mathrm{s})+\mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{~s}) \longrightarrow \mathrm{CaCl}_{2}(\mathrm{~s})+2 \mathrm{NH}_{3}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})$

$Q.16 Ethylene glycol is used as automobile antifreeze. It has 38.7 \% carbon 9.7 \% hydrogen and 51.6 \% oxygen. Its molar mass is 62.1 \mathrm{~g} \mathrm{~mol}^{-1} . Determine its empirical formula.?(Ans: \mathrm{CH}_{3} \mathrm{O} )$

$Q.7 Boron with atomic number 5 has two naturally occurring isotopes. Calculate the percentage abundance of { }^{10} \mathrm{~B} and { }^{11} \mathrm{~B} from the following information.Average atomic mass of boron =10.81 \mathrm{amu} Isotopic mass of { }^{10} \mathrm{~B} =10.0129 \mathrm{amu} Isotopic mass of { }^{\prime \prime} \mathrm{B} =11.0093 \mathrm{amu} (Ans: 20.002 \% 79.992 \% )$

$Q.5(a) What are isotopes? How do you deduce the fractional atomic masses of elements from the relative isotopic abundance? Give two examples in support of your answer.$

$Q.25 Explain the following with reasons.i) Law of conservation of mass has to be obeyed during stoichiometric calculations.$

$Calculate the number of grams of \mathrm{K}_{2} \mathrm{SO}_{4} and water produced when 14 \mathrm{~g} of \mathrm{KOH} are reacted with excess of \mathrm{H}_{2} \mathrm{SO}_{4} . Also calculate the number of molecules of water produced.$

$Define the following terms and give three examples of each.(i) Gram atom$