Chemistry Questions & Answers

Lattice enthalpy for NaCl is \( +788 \mathrm{~kJ} \mathrm{~mol}^{-1} \) and \( \Delta_{\mathrm{Hyd}}^{\circ}=-784 \mathrm{~kJ} \mathrm{~mol}^{-1} \). Enthalpy of solution of \( \mathrm{NaCl}^{\circ} \) is \( \begin{array}{ll}\text { (a) }+572 \mathrm{~kJ} \mathrm{~mol}^{-1} & \text { (b) }+4 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \text { (c) }-572 \mathrm{~kJ} \mathrm{~mol}^{-1} & \text { (d) }-4 \mathrm{~kJ} \mathrm{~mol}^{-1}\end{array} \)

A certain reaction is non spontancous at 298 K . The entropy change during the reaction is \( 121 \mathrm{JK}^{-1} \). Is the reaction is endothermic or exothermic? The minimum value of \( \Delta \mathrm{H} \) for the reaction is (a) endothermic, \( \Delta \mathrm{H}=36.06 \mathrm{~kJ} \) (b) exothermic, \( \Delta \mathrm{H}=-36.06 \mathrm{~kJ} \) (c) endothermic, \( \Delta \mathrm{H}=60.12 \mathrm{~kJ} \) (d) exothermic, \( \Delta \mathrm{H}=-60.12 \mathrm{~kJ} \)

2 mole of an ideal gas at \( 27^{\circ} \mathrm{C} \) temperature is expanded reversibly from 2 lit to 20 lit. Find the entropy change. \( (R=2 \mathrm{cal} / \mathrm{mol} \mathrm{K}) \) \( \begin{array}{llll}\text { (a) } 92.1 & \text { (b) } 0 & \text { (c) } 4 & \text { (d) }-9.2\end{array} \)

What is the entropy change (in \( \mathrm{JK}^{-1} \mathrm{~mol}^{-1} \) ) when one mole of ice is converted into water at \( 0^{\circ} \mathrm{C} \) ? (The enthalpy change for the conversion of ice to liquid water is \( 6.0 \mathrm{~kJ} \mathrm{~mol}^{-1} \) at \( 0^{\circ} \mathrm{C} \) ) \( \begin{array}{llll}\text { (a) } 21.98 & \text { (b) } 20.13 & \text { (c) } 2.013 & \text { (d) } 2.198\end{array} \)

The molar entropies of \( \mathrm{HI}(\mathrm{g}) \) and \( \mathrm{I}(\mathrm{g}) \) at 298 K are 206.5 114.6 , and \( 180.7 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1} \) respectively. Using the \( \Delta \mathrm{G}^{\circ} \) given below, calculate the bond energy of HI . \( \mathrm{HI}(\mathrm{g}) \longrightarrow \mathrm{H}(\mathrm{g})+\mathrm{I}(\mathrm{g}) ; \Delta \mathrm{G}^{\circ}=271.8 \mathrm{~kJ} \) \( \begin{array}{ll}\text { (a) } 282.4 \mathrm{~kJ} \mathrm{~mol}^{-1} & \text { (b) } 298.3 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \text { (c) } 290.1 \mathrm{~kJ} \mathrm{~mol}^{-1} & \text { (d) } 315.4 \mathrm{~kJ} \mathrm{~mol}^{-1}\end{array} \)

Which pair of chemicals is capable of forming a buffer solution? (A) HCl and NaCl (B) \( \mathrm{HNO}_{2} \) and KNO 2 (C) KCl and NaF (D) HBr and \( \mathrm{NH}_{3} \)

Questions Check Answers How many milliliters of a 6.0 M HCl solution will provide 164 g of HCl ? Answer: 750 mL of HCl solution

A 28.95 mL sample of HCl of unknown concentration is transferred to a flask, where a few drops of indicator solution are added. The solution is titrated with 1.9 M NaOH . After 11.5 mL are added, the indicator turns pink, showing that the equivalence point has been reached. Calculate the molarity of the acid.

Question 8 What is the pH of a solution with \( \mathrm{pOH}=8.13 \) ? Add your answer

Buttermilk is the example of homogeneous or heterogeneous mixture?