Exam Notes - Multiple Choice Questions

Multiple Choice

1. Methanethiol (CH4S) Composition

   • A molecule of methanethiol (CH4S) consists of:

     • 1 atom of Carbon (C)

     • 4 atoms of Hydrogen (H)

     • 1 atom of Sulfur (S)

2. Significant Figures

   • A measurement labeled "100 g sugar" has a definite number of significant figures, which is 3. The zeroes are considered significant because they are not just placeholders. However, without further context it is hard to determine. In this case, it is most likely that the number of significant figures in the measurement is 3.

3. Bicycle as a Compound

   • Analogy: Bicycle components as elements in a compound.

   • Components:

     • 2 Wheels (W)

     • 2 Pedals (P)

     • 1 Seat (S)

     • 1 Frame (F)

   • Chemical formula: $FW<em>2P</em>2S$

4. Moles of Bicycle Components

   • To assemble 1 mole of the bicycle:

     • You need $2 \times 6.022 \times 10^{23}$ wheels.

     • You need $2 \times 6.022 \times 10^{23}$ pedals.

     • You need $1 \times 6.022 \times 10^{23}$ seats.

     • You need $1 \times 6.022 \times 10^{23}$ frames.

     • This corresponds to $12.044 \times 10^{23}$ wheels, $12.044 \times 10^{23}$ pedals, $6.022 \times 10^{23}$ seats, and $6.022 \times 10^{23}$ frames.

5. Limiting Reactant Problem (Bicycles)

   • Given:

     • 50 wheels

     • 25 pedals

     • 50 seats

     • 20 frames

   • Bicycle requires 2 wheels, 2 pedals, 1 seat, and 1 frame.

   • Calculation:

     • Wheels: 50 wheels / 2 wheels per bicycle = 25 bicycles

     • Pedals: 25 pedals / 2 pedals per bicycle = 12.5 bicycles

     • Seats: 50 seats / 1 seat per bicycle = 50 bicycles

     • Frames: 20 frames / 1 frame per bicycle = 20 bicycles

   • The limiting reactant is the number of pedals, allowing only 12 complete bicycles to be assembled.

6. Nitric Acid (HNO3) Synthesis

   • Reaction: $N<em>2(g) + 2O</em>2(g) + 2H<em>2O \rightarrow 2HNO</em>3$

   • If you have $6.022 \times 10^{23}$ molecules of each reactant:

     • $N_2$: $6.022 \times 10^{23}$ molecules (1 mole)

     • $O_2$: $6.022 \times 10^{23}$ molecules (1 mole)

     • $H_2O$: $6.022 \times 10^{23}$ molecules (1 mole)

   • Since 1 mole of $N<em>2$ requires 2 moles of $O</em>2$ and 2 moles of $H<em>2O$ to produce 2 moles of $HNO</em>3$, $N_2$ is the limiting reactant.

   • Therefore, only 2 moles of $HNO_3$ can be produced.

7. Chlorate Ion Formula

   • Chlorate ion formula: $ClO_3^-$

8. Perchlorate Ion Formula

   • Perchlorate ion formula: $ClO_4^-$

9. Hypochlorite Ion Formula

   • Hypochlorite ion formula: $ClO^-$