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?
Here is a worked example of a stoichiometry problem. Just follow the steps. After moles HCN are calculated, remember 1 mole of a gas occupies 22.4 L at STP.
http://www.jiskha.com/science/chemistry/stoichiometry.html
I am having trouble balancing this reaction!
To calculate the volume of gas evolved, we need to determine the moles of the reactants and then use the stoichiometry of the balanced equation to find the moles of gas produced. Finally, we can convert the moles of gas to liters at STP (Standard Temperature and Pressure).
1. Start by calculating the moles of magnesium bicarbonate (Mg(HCO3)2) and hydrocyanic acid (HCN) present in the given quantities.
- The molar mass of magnesium bicarbonate (Mg(HCO3)2) is:
Mg = 24.31 g/mol
H = 1.01 g/mol
C = 12.01 g/mol
O = 16.00 g/mol
So, the molar mass of Mg(HCO3)2 is: 24.31 + (2 * (1.01 + 12.01 + 3 * 16.00)) = 146.4 g/mol.
- The moles of Mg(HCO3)2 can be calculated using its molar mass and the given mass of 7.76 grams:
moles of Mg(HCO3)2 = mass / molar mass
moles of Mg(HCO3)2 = 7.76 g / 146.4 g/mol
- Next, calculate the moles of hydrocyanic acid (HCN) using the given volume and concentration:
moles of HCN = volume (in L) * concentration (in mol/L)
moles of HCN = 0.300 L * 0.10 mol/L
2. After determining the moles of Mg(HCO3)2 and HCN, we need to check the balanced chemical equation to find the stoichiometry. The balanced equation for the reaction between magnesium bicarbonate and hydrocyanic acid is:
Mg(HCO3)2 + 2 HCN -> 2 CO2 + 2 H2O + Mg(CN)2
From the balanced equation, we can see that for every mole of Mg(HCO3)2, 2 moles of CO2 are produced.
3. Calculate the moles of CO2 produced using the stoichiometry determined from the balanced equation.
- Moles of CO2 produced = Moles of Mg(HCO3)2 * (2 moles of CO2 / 1 mole of Mg(HCO3)2)
4. Convert the moles of CO2 to liters of gas at STP.
- At STP, one mole of gas occupies 22.4 liters.
- Calculate the volume of gas produced at STP by multiplying the moles of CO2 by 22.4 liters/mole.
Follow these steps to calculate the volume of gas evolved at STP.