Calculate the sodium ion concentration when 70 ml of 3.M sodium carbonate is added to 30 ml of 1.M sodium bicarbonate.
moles Na in Na2CO3 = M x L x 2 = ??
moles Na in NaHCO3 = M x L = ??
Total Na = moles Na in #1 + moles Na in #2. then concn Na = moles/L soln.
To calculate the sodium ion concentration after mixing sodium carbonate and sodium bicarbonate, we need to use the concept of moles and the balanced chemical equation.
First, let's determine the moles of sodium carbonate and sodium bicarbonate in their respective solutions:
Moles of sodium carbonate = volume (in liters) × molarity
Moles of sodium carbonate = 70 ml × (1 L/1000 ml) × 3 M = 0.21 moles
Moles of sodium bicarbonate = 30 ml × (1 L/1000 ml) × 1 M = 0.03 moles
Next, we need to understand the chemical reaction between sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3). When these two compounds react, they form sodium ions (Na+) along with other products.
The balanced chemical equation for the reaction is:
Na2CO3 + 2 NaHCO3 → 3 Na+ + 3 CO3-2 + H2O + CO2
From the equation, we can see that for each molecule of sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3), we get three sodium ions (3 Na+).
To calculate the total sodium ion concentration, we need to add the moles of sodium carbonate and sodium bicarbonate and then multiply by three to account for the ratio of sodium ions:
Total moles of sodium ions = (moles of sodium carbonate + moles of sodium bicarbonate) × 3
Total moles of sodium ions = (0.21 moles + 0.03 moles) × 3 = 0.78 moles
Finally, to find the concentration, we divide the total moles of sodium ions by the total volume of the mixture:
Concentration of sodium ions = Total moles of sodium ions / Total volume of mixture
Concentration of sodium ions = 0.78 moles / (70 ml + 30 ml) = 0.78 moles / 100 ml
Since the concentration is usually expressed in M (moles per liter), we convert the volume from milliliters to liters:
Concentration of sodium ions = 0.78 moles / (100 ml) × (1 L / 1000 ml) = 0.0078 M
Therefore, the sodium ion concentration after mixing the solutions is 0.0078 M.