When 7.76 grams of magnesium bicarbonate are mixed with 300. mL of 0.10 M hydrocyanic acid, how many liters of gas are evolved at STP?
To determine the number of liters of gas evolved at STP, we first need to calculate the amount of gas produced using the given information.
1. The equation for the reaction between magnesium bicarbonate and hydrocyanic acid is:
Mg(HCO3)2 + 2HCN -> Mg(CN)2 + 2H2O + 2CO2
2. Calculate the moles of magnesium bicarbonate:
Given mass of magnesium bicarbonate = 7.76 grams
Molar mass of magnesium bicarbonate (Mg(HCO3)2) = 146.28 g/mol
Moles of magnesium bicarbonate = mass / molar mass
= 7.76 g / 146.28 g/mol
3. Calculate the moles of hydrocyanic acid:
Given volume of hydrocyanic acid = 300 mL = 0.3 L
Molarity of hydrocyanic acid (HCN) = 0.10 M
Moles of hydrocyanic acid = volume(L) × concentration(M)
= 0.3 L × 0.10 mol/L
4. The stoichiometry of the reaction tells us that 1 mole of magnesium bicarbonate reacts with 2 moles of hydrocyanic acid to produce 2 moles of carbon dioxide gas (CO2).
Therefore, the number of moles of CO2 produced is half the number of moles of hydrocyanic acid used.
5. Now that we have the number of moles of CO2, we can calculate the volume of gas evolved at STP. The molar volume of an ideal gas at STP is 22.4 L/mol.
Moles of carbon dioxide gas = (1/2) × moles of hydrocyanic acid
Volume of carbon dioxide gas at STP = moles of CO2 × molar volume
By following the above steps and calculating the moles of CO2 produced, you can determine the number of liters of gas evolved at STP.