2. Chemical reactions involve the breaking of chemical bonds in the reactants and the formation of chemical bonds in the Circle the correct answer. products reactants Is the following sentence true or false? The formation of chemical bonds absorbs energy. Is the following sentence true or false? The heat and light given off by a propane stove result from the formation of new chemical bonds. The combustion of one molecule of propane \( \left(\mathrm{C}_{3} \mathrm{H}_{8}\right) \) results in the formation of \( 6 \mathrm{C}=\mathrm{O} \) double bonds and \( 8 \quad \mathrm{H} \) single bonds.

5) \( \mathrm{Ag}_{2} \mathrm{O} \rightarrow \)

Questão 1) São dadas as seguintes equações termoquímicas: \( \begin{array}{l}\text { I) } \mathrm{C}_{(\mathrm{s})}+\mathrm{O}_{2(\mathrm{~g})} \longrightarrow \mathrm{CO}_{2(\mathrm{~g})} \quad \Delta \mathrm{H}=-94,1 \mathrm{kcal} / \mathrm{mol} \\ \begin{array}{l}\text { II) } \mathrm{H}_{2(\mathrm{~g})}+1 / 2 \mathrm{O}_{2(\mathrm{~g})}\end{array} \longrightarrow \mathrm{H}_{2} \mathrm{O}_{(\mathrm{l})} \quad \Delta \mathrm{H}=-68,3 \mathrm{kcal} / \mathrm{mol} \\ \text { III) } \mathrm{C}_{(\mathrm{s})}+2 \mathrm{H}_{2(\mathrm{~g})} \longrightarrow \mathrm{CH}_{4(\mathrm{~g})} \quad \Delta \mathrm{H}=-17,9 \mathrm{kcal} / \mathrm{mol} \\ \text { Calcule o calor liberado, em kcal, na reação de combustão de } 1 \text { mol de gás metano. } \\ \mathrm{CH}_{4(\mathrm{~g})}+2 \mathrm{O}_{2(\mathrm{~g})} \longrightarrow \mathrm{CO}_{2(\mathrm{~g})}+2 \mathrm{H}_{2} \mathrm{O}_{(\mathrm{l})} \quad \Delta \mathrm{H}=\text { ? }\end{array} \$ \begin{array}{l}\longrightarrow\end{array} \)

14 Nitrogen has atomic number 7 and oxygen has atomic number 8 What is total number of electrons in \( \left(\mathrm{NO}_{3}\right)^{-} \)ion ? \( \begin{array}{ll}\text { (a) } 15 \mathrm{e}^{-} & \text {(b) } 31 \mathrm{e}^{-} \\ \text {(c) } 32 \mathrm{e}^{-} & \text {(d) } 46 \mathrm{e}^{-}\end{array} \)

possible Find the hydrogen ion concentration of a solution whose pH is 7.1 . Use the formula \( \mathrm{pH}=-\log \left[\mathrm{H}^{+}\right] \)

Consider the same reaction as in question 6 above: \[ 4 \mathrm{Al}(s)+3 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{Al}_{2} \mathrm{O}_{3}(s) \] How many grams of aluminum oxide will be produced from the complete reaction of 1.27 L of oxygen gas at 783.0 mmHg and \( 30.0^{\circ} \mathrm{C} \) ?