Tooth enamel is the hardest substance in the body and is mainly the mineral hydr

Question

Tooth enamel is the hardest substance in the body and is mainly the mineral hydroxyapatite, Ca_10(PO_4)_6(OH)_2. If 1.000 g of tooth enamel reacts with hydrochloric acid to give 0.925 g of CaCl_2, what is the percentage of hydroxyapatite in tooth enamel? Ca_10(PO_4)_6 (OH)_2 (s) + 20 HCI(aq) rightarrow 10 CaCl_2(aq) + 6 H_3PO_4(aq) + 2H_2O(l) Milk of magnesia, Mg(OH)_2, is prepared from magnesium sulfate and sodium hydroxide. If a solution containing 100.0 g of MgSO_4 is added to a solution with 70.0 g of NaOH, what is the limiting reactant? Calculate the mass of milk of magnesia produced. MgSO_4(aq) + 2NaOH(aq) rightarrow Mg(OH)_2(s) + Na_2SO_4(aq)

Explanation / Answer

m = 1 g of enamel

m = HCl

m = 0.925 g of CaCl2

mol of CaCl2 = mass/MW = 0.925/110.98 = 0.0083348351 mol of CaCl2

then

since ratio is 1:10

0.0083348351/10 = 0.00083348351 mol of hydroxylapatite

MW = 502.3114 g/mol

mass = mol*MW= 502.3114 *0.00083348351 = 0.4186 g of Hydrylapattite

then

% = 0.4186 /1*100 = 41.86% is hydroxylapathite

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