5. ตอบคำถามต่อไปนี้ 1) สารละลายกรดแอซีติกเข้มข้น 0.2 โมล/ลูกบาศก์เดซิเมตร \( \left(\mathrm{K}_{\mathrm{a}}=1.8 \times 10^{-5}\right) \) จะมีไฮโดรเนียม ไอออนเข้มข้นกี่โมล/ลูกบาศก์เดซิเมตร

Based on bond type, which compound has the highest melting point? 1. \( \mathrm{CH}_{3} \mathrm{OH} \) 2. \( \mathrm{C}_{6} \mathrm{H}_{14} \) 3. \( \mathrm{CaCl}_{2} \) 4. \( \mathrm{CCl}_{4} \)

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 \( 30.0^{\circ} \mathrm{C} \) ?

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

3.48 The empirical formula of a compound is CH . If the molar mass of this compound is about 78 g , what is its molecular formula?

Which fermula represents an ionic compound? 1. \( \mathrm{H}_{2} \) 2. \( \mathrm{CH}_{4} \) 3. \( \mathrm{CH}_{3} \mathrm{OH} \) 4. \( \mathrm{NH}_{4} \mathrm{Cl} \)