Question

1. what is the molar mass of \\(\text{nahco}_3\\)?

1. how can you tell if you are going to have a covalent or ionic bond?

1. aluminum reacts with oxygen to form aluminum oxide. which best represents this reaction?

a) \\(2\text{al}_{(\text{s})} + \text{o}_{2(\text{g})} \
ightarrow 2\text{alo}\\)
b) \\(4\text{al}_{(\text{s})} + 3\text{o}_{2(\text{g})} \
ightarrow 2\text{al}_2\text{o}_{3(\text{s})}\\)
c) \\(\text{al}_{2(\text{s})} + \text{o}_{2(\text{g})} \
ightarrow \text{al}_2\text{o}_{2(\text{s})}\\)
d) \\(\text{al}_{(\text{s})} + \text{o}_{(\text{g})} \
ightarrow \text{alo}_{(\text{s})}\\)

1. what do the abbreviations s, l, aq, g mean in a reaction?

1. what is the molar concentration (i.e. the molarity) of a solution if 0.3 moles of \\(\text{nh}_3\\) is dissolved in 250ml of water?

1. what volume does 0.500 mol. of methane gas occupy at s.t.p.?

Explanation:

Calculate molar mass of sodium bicarbonate

We sum the atomic masses of all atoms in the chemical formula \( \text{NaHCO}_3 \).
Using standard atomic masses:

• \( \text{Na} = 22.990 \text{ g/mol} \)
• \( \text{H} = 1.008 \text{ g/mol} \)
• \( \text{C} = 12.011 \text{ g/mol} \)
• \( \text{O} = 3 \times 15.999 = 47.997 \text{ g/mol} \)

Summing these values:

$$ \text{Molar Mass} = 22.990 + 1.008 + 12.011 + 47.997 = 84.006 \text{ g/mol} $$

Distinguish ionic and covalent bonds

We identify the types of elements involved in the bonding:

• Ionic Compounds are formed when a metal transfers electrons to a non-metal.
• Covalent bonds are formed when two non-metals share electrons.

Identify the balanced reaction for aluminum oxide

Aluminum (\(\text{Al}\)) reacts with oxygen gas (\(\text{O}_2\)) to form aluminum oxide (\(\text{Al}_2\text{O}_3\)).
Using Chemical Equation Balancing, we balance the atoms on both sides:

$$ 4\text{Al(s)} + 3\text{O}_2\text{(g)} ightarrow 2\text{Al}_2\text{O}_3\text{(s)} $$

This matches option (b).

Define state abbreviations in reactions

These abbreviations represent the physical states of the substances:

• \(\text{s}\): solid
• \(\text{l}\): liquid
• \(\text{aq}\): aqueous (dissolved in water)
• \(\text{g}\): gas

Calculate molar concentration of ammonia

Molarity (\(M\)) is defined as moles of solute per liter of solution:

$$ M = \frac{\text{moles of solute}}{\text{liters of solution}} $$

Convert volume to liters:

$$ 250 \text{ mL} = 0.250 \text{ L} $$

Calculate concentration:

$$ M = \frac{0.3 \text{ mol}}{0.250 \text{ L}} = 1.2 \text{ M} $$

Calculate gas volume at STP

At Standard Temperature and Pressure (STP), 1 mole of any ideal gas occupies a molar volume of \(22.4 \text{ L}\).
Using this relationship:

$$ \text{Volume} = 0.500 \text{ mol} \times 22.4 \text{ L/mol} = 11.2 \text{ L} $$

Answer:

Question 10

The molar mass of \( \text{NaHCO}_3 \) is \( 84.006 \text{ g/mol} \).

Question 11

• Ionic bond: Formed between a metal and a non-metal (via electron transfer).
• Covalent bond: Formed between two non-metals (via electron sharing).

Question 12

• a) 2 Al(s) + O2(g) -> 2 AlO
• b) 4Al(s) + 3 O2(g) -> 2 Al2O3(s) (Correct answer)
• c) Al2(s) + O2(g) -> Al2O2(s)
• d) Al(s) + O(g) -> AlO(s)

Question 13

• s: solid
• l: liquid
• aq: aqueous (dissolved in water)
• g: gas

Question 14

The molar concentration of the solution is \( 1.2 \text{ M} \) (or \( 1.2 \text{ mol/L} \)).

Question 15

The volume occupied by the gas at STP is \( 11.2 \text{ L} \).