91Ó°ÊÓ

Convert the following into basic units: (i) \(\quad 28.7 \mathrm{pm}\) (ii) \(15.15 \mathrm{pm}\) (iii) \(\quad 25365 \mathrm{mg}\)

Which one of the following will have the largest number of atoms? (i) \(1 \mathrm{~g} \mathrm{Au}(\mathrm{s})\) (ii) \(1 \mathrm{~g}\) Na (s) (iii) \(\quad 1\) g Li (s) (iv) \(\quad 1 \mathrm{~g}\) of \(\mathrm{Cl}_{2}(\mathrm{~g})\)

How many significant figures should be present in the answer of the following calculations? (i) \(\frac{0.02856 \times 298.15 \times 0.112}{0.5785}\) (ii) \(5 \times 5.364\) (iii) \(\quad 0.0125+0.7864+0.0215\)

Use the data given in the following table to calculate the molar mass of naturally occuring argon isotopes: \(\begin{array}{lll}\text { Isotope } & \text { Isotopic molar mass } & \text { Abundance } \\ { }^{36} \mathrm{Ar} & 35.96755 \mathrm{~g} \mathrm{~mol}^{-1} & 0.337 \% \\ { }^{38} \mathrm{Ar} & 37.96272 \mathrm{~g} \mathrm{~mol}^{-1} & 0.063 \% \\ { }^{40} \mathrm{Ar} & 39.9624 \mathrm{~g} \mathrm{~mol}^{-1} & 99.600 \%\end{array}\)

A welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives \(3.38 \mathrm{~g}\) carbon dioxide, \(0.690 \mathrm{~g}\) of water and no other products. A volume of \(10.0 \mathrm{~L}\) (measured at STP) of this welding gas is found to weigh \(11.6 \mathrm{~g}\). Calculate (i) empirical formula, (ii) molar mass of the gas, and (iii) molecular formula.

A welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives \(3.38 \mathrm{~g}\) carbon dioxide, \(0.690 \mathrm{~g}\) of water and no other products. A volume of \(10.0 \mathrm{~L}\) (measured at STP) of this welding gas is found to weigh \(11.6 \mathrm{~g}\). Calculate (i) empirical formula, (ii) molar mass of the gas, and (iii) molecular formula.

Chlorine is prepared in the laboratory by treating manganese dioxide \(\left(\mathrm{MnO}_{2}\right)\) with aqueous hydrochloric acid according to the reaction \(4 \mathrm{HCl}(\mathrm{aq})+\mathrm{MnO}_{2}(\mathrm{~s}) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{MnCl}_{2}(\mathrm{aq})+\mathrm{Cl}_{2}(\mathrm{~g})\) How many grams of \(\mathrm{HCl}\) react with \(5.0 \mathrm{~g}\) of manganese dioxide?