Final answer:
To calculate the volume of carbon (IV) oxide evolved at s.t.p when 21g of sodium hydrogen trioxocarbonate (IV) is heated, use the balanced equation and mole ratios to find the moles of CO2, then convert to volume using the ideal gas law.
Step-by-step explanation:
To calculate the volume of carbon (IV) oxide evolved at s.t.p when 21g of sodium hydrogen trioxocarbonate (IV) is heated, we first need to balance the equation for the reaction. The balanced equation is: 2NaHCO3 -> Na2CO3 + CO2 + H2O.
According to the balanced equation, for every 2 moles of NaHCO3, 1 mole of CO2 is produced. Therefore, to find the moles of CO2 produced, we can use the mole ratio:
21g NaHCO3 * (1 mol NaHCO3 / 84g NaHCO3) * (1 mol CO2 / 2 mol NaHCO3) = 0.125 mol CO2
Since this reaction is at standard temperature and pressure (STP), one mole of any ideal gas occupies a volume of 22.4 dm³. Therefore, the volume of carbon (IV) oxide evolved at s.t.p when 21g of sodium hydrogen trioxocarbonate (IV) is heated is 0.125 mol * 22.4 dm³/mol = 2.8 dm³.