Exercice 6 La combustion dans du dioxygène de \( 0,295 \mathrm{~g} \) d'une substance donne \( -0,440 \mathrm{~g} \) de dioxyde de carbone -0,210g d'eau L'analyse effectuée sur la même másse fournit \( 37,00 \mathrm{~mL} \) de diazote, volume mesuré dans les CNTP \( 1^{\circ} \) ) Sachant que le composé renferme essentiellement du carbone, de l'hydrogène, de l'oxygène et de l'azote, déterminer sa composition centésimale massique \( 2^{\circ} \) ) Trouver sa formule brute sachant que la molécule ne renferme qu'un atome d'azote

5. At what pressure will 7.89 g of ammonia gas, \( \mathrm{NH}_{3} \), occupy 7.46 L at \( 20.0^{\circ} \mathrm{C} \) ?

6. Aluminum reacts with oxygen according to the following reaction: \[ 4 \mathrm{Al}(s)+3 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{Al}_{2} \mathrm{O}_{3}(s) \] How many liters of oxygen gas at STP are required to completely react with 55.0 g of aluminum?

10 Essay 5 points Please identify the following components for the element Selenium: 1 Chemical Symbol 2. Atomic Number 3. Family \# 4. Valence Electrons 5. Category Edit View Insert Format Tools Table

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

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 ? \( \begin{array}{ll}\text { (a) } 15 \mathrm{e}^{-} & \text {(b) } 31 \mathrm{e}^{-} \\ \text {(c) } 32 \mathrm{e}^{-} & \text {(d) } 46 \mathrm{e}^{-}\end{array} \)