Calcium dihydrogen phosphate, Ca(H2PO4)2, and sodium hydrogen carbonate, NaHCO3,
ID: 565652 • Letter: C
Question
Calcium dihydrogen phosphate, Ca(H2PO4)2, and sodium hydrogen carbonate, NaHCO3, are ingredients of baking powder that react with each other to produce CO2, which causes dough or batter to rise: Ca(H2PO4)2(s) + NaHCO3(s) CO2(g) + H2O(g) + CaHPO4(s) + Na2HPO4(s)[unbalanced] If the baking powder contains 31.0% NaHCO3 and 35.0% Ca(H2PO4)2 by mass:
(a) How many moles of CO2 are produced from 8.67 g of baking powder?
(b) If 1 mol of CO2 occupies 37.0 L at 350°F (a typical baking temperature), what volume of CO2 is produced from 8.67 g of baking powder?
Explanation / Answer
a)
The balanced equation of reaction between Calcium dihydrogen phosphate, Ca(H2PO4)2, and sodium hydrogen carbonate, NaHCO3 is written as follows:
Ca(H2PO4)2(s) + 2 NaHCO3(s) ------> 2CO2(g) + 2H2O(g) + CaHPO4(s) + Na2HPO4(s)
Thus, one mole of Ca(H2PO4)2 reacts with two moles of NaHCO3 to produce two moles of CO2.
Baking powder contains 31% NaHCO3 and 35% Ca(H2PO4)2. Therefore, 8.67 g of baking powder will contain (8.67 x 0.31)g of NaHCO3 and (8.67 x 0.35)g of Ca(H2PO4)2
Molar mass of Ca(H2PO4)2 is 234.05 g/mol. Calculate amount of CO2 produced.
Amount of CO2 produced by (8.67 x 0.35)g of Ca(H2PO4)2 = (2 mol/1mol) x ((8.67 x 0.35)g / 234.05 g/mol)
Amount of CO2 produced by (8.67 x 0.35)g of Ca(H2PO4)2 = 0.02593 mol
Molar mass of NaHCO3 is 84.007 g/mol. Calculate amount of CO2 produced.
Amount of CO2 produced by (8.67 x 0.31)g g of NaHCO3 = (2 mol / 2 mol) x ((8.67 x 0.31)g / 84.007 g/mol)
Amount of CO2 produced by (8.67 x 0.31)g g of NaHCO3 = 0.03199 mol
Amount of CO2 produced from Ca(H2PO4)2 is less than that produced from NaHCO3. Thus, limiting reagent is Ca(H2PO4)2 and amount of CO2 produced by 8.67g of baking powder is 0.02593 moles.
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b)
The volume occupied by 1 mole of CO2 is 37.0 L at 350 oF. Calculate volume occupied by 0.02593 moles of CO2.
Volume of 0.02593 moles of CO2 = (37.0 L / 1 mol) x 0.02593 mol
Volume of 0.02593 moles of CO2 = 0.959 L
Therefore, 8.67 of baking powder produces 0.959 L of CO2 at 350 oF