Let's solve the questions step by step:
a. Sodium hydrogencarbonate decomposes on heating.
The balanced equation is: \[ 2 \text{NaHCO}_3(s) \rightarrow \text{Na}_2\text{CO}_3(s) + \text{H}_2\text{O}(g) + \text{CO}_2(g) \]
i. The number of moles of sodium hydrogencarbonate used:
To find the number of moles, you can use the formula: \[ \text{Number of moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \]
Molar mass of NaHCO₃:
- Sodium (Na): 23 g/mol
- Hydrogen (H): 1 g/mol
- Carbon (C): 12 g/mol
- Oxygen (O): 16 g/mol × 3 = 48 g/mol
- Total: \( 23 + 1 + 12 + 48 = 84 \text{ g/mol} \)
Now, calculate the number of moles of sodium hydrogencarbonate: \[ \text{Number of moles} = \frac{3.36 \text{ g}}{84 \text{ g/mol}} = 0.04 \text{ moles} \]
Answer: 0.04 moles of sodium hydrogencarbonate.
ii. The number of moles of sodium carbonate produced:
According to the balanced equation, 2 moles of NaHCO₃ yield 1 mole of Na₂CO₃. Therefore, the number of moles of Na₂CO₃ produced can be calculated from the moles of NaHCO₃ used: \[ \text{Moles of Na}_2\text{CO}_3 = \frac{0.04 \text{ moles of NaHCO}_3}{2} = 0.02 \text{ moles} \]
Answer: 0.02 moles of sodium carbonate produced.
iii. The mass of sodium carbonate produced:
To find the mass of sodium carbonate, we first need to find its molar mass.
Molar mass of Na₂CO₃:
- Sodium (Na): 23 g/mol × 2 = 46 g/mol
- Carbon (C): 12 g/mol
- Oxygen (O): 16 g/mol × 3 = 48 g/mol
- Total: \( 46 + 12 + 48 = 106 \text{ g/mol} \)
Now calculate the mass: \[ \text{Mass} = \text{Number of moles} \times \text{Molar mass} \] \[ \text{Mass of Na}_2\text{CO}_3 = 0.02 \text{ moles} \times 106 \text{ g/mol} = 2.12 \text{ g} \]
Answer: 2.12 g of sodium carbonate produced.
b. If 2.1 kg (2100 g) of sodium hydrogencarbonate is heated, calculate the mass of CO₂ produced.
First, calculate the number of moles of NaHCO₃ in 2100 g: \[ \text{Number of moles of NaHCO}_3 = \frac{2100 \text{ g}}{84 \text{ g/mol}} = 25 \text{ moles} \]
From the balanced equation, 2 moles of NaHCO₃ produce 1 mole of CO₂, which means: \[ \text{Moles of CO}_2 = \frac{25 \text{ moles of NaHCO}_3}{2} = 12.5 \text{ moles} \]
Now, calculate the mass of CO₂ produced: Molar mass of CO₂:
- Carbon (C): 12 g/mol
- Oxygen (O): 16 g/mol × 2 = 32 g/mol
- Total: \( 12 + 32 = 44 \text{ g/mol} \)
Now calculate the mass: \[ \text{Mass of CO}_2 = \text{Number of moles} \times \text{Molar mass} = 12.5 \text{ moles} \times 44 \text{ g/mol} = 550 \text{ g} \]
Answer: 550 g of CO₂ produced.
c. Explain how sodium hydrogen carbonate makes the batter rise.
Sodium hydrogen carbonate (bicarbonate of soda) is a chemical leavening agent. When it is mixed with an acid and heated, it decomposes and releases carbon dioxide gas:
- The reaction between the bicarbonate and the acid produces CO₂ gas when the batter is heated.
- The released CO₂ gas forms bubbles within the batter.
- As the batter heats up in the oven, the CO₂ gas expands, causing the batter to rise and resulting in a light and fluffy texture in baked goods.
Answer: Sodium hydrogen carbonate releases carbon dioxide gas when heated or reacts with an acid, forming bubbles in the batter, which makes it rise and become light and fluffy during baking.