Rhubarb leaves contain 0.520 g of oxalic acid (H2C202) per 100.0 g of leaves. Ox

Question

Rhubarb leaves contain 0.520 g of oxalic acid (H2C202) per 100.0 g of leaves. Oxalic acid can react with calcium ion, forming insoluble calcium oxalate, which is a major component of kidney stones. Write a balanced equation for the reaction of aqueous oxalic acid with aqueous calcium hydroxide. Indicate all states for reagents/products. If 375 ml of a 0.866 M solution of oxalic acid is treated with excess 0.133 M calcium hydroxide, how much calcium oxalate is formed? Show all work. .What volume of calcium hydroxide solution is required to be present in a 20% excess to ensure complete reaction? Show all work. What mass of rhubarb leaves are required to prepare the oxalic acid solution in Question 2, assuming 75% yield for the extraction? Show all work. .

Explanation / Answer

a)

H2C2O4 + Ca(OH)2 = C2O4-+ 2H2O + Ca+

or

H2C2O4 + Ca(OH)2 = CaC2O4 + 2H2O

b)

mol of acid = MV = 0.866*375*10^-3 =0.32475

mol of CaC2O4 formed --> 0.32475mol

since raito is 1:1

C)

20$ excess to ensure copmlete reaction

0.32475 mol --> 0.32475*1.2 = 0.3897 mol of Ca(OH)2 required

V = mol/V = 0.3897 / 0.133

V = 2.930 L required

d

0.32475 mol of acid required

100 g = 0.52 g

mass of H2C2O4 = 0.32475 mol --> 90.03 *0.32475 = 29.237 g

then... if 75% yield --> 29.237/0.75 = 38.9826 g of acid required

0.52 g present in 100 g

38.9826 g of acid --> x

x = 38.9826*100/0.52

x = 7496.6 g

x = 7.5 kg approx of leaves

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