Chemistry Homework week 3-4

# Chemistry Homework week 3-4 - 3.41 Cinnamic alcohol is used...

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3.41 Cinnamic alcohol is used mainly in perfumery, particularly in soaps and cosmetics. Its molecular formula is C<sub>9</sub>H<sub>10</sub>O. (a) Calculate the percent composition by mass of C, H and O in cinnamic alcohol. (b) How many molecules of cinnamic alcohol are contained in a sample mass of 0.469g? ANSWER: (a) Molar Mass C<sub>9</sub>H<sub>10</sub>O= 9(12.01g)+ 10(1.008g)+ 16g = 134.17g %C = 9(12.01g)/134.17g x 100% = 80.56% %H = 10(1.008g)/134.17g x 100% = 7.51% %O = 16g/134.17g x 100% = 11.93% (b) 0.469g x ( 1 mol C<sub>9</sub>H<sub>10</sub>O/134.17g)x (6.022x10<sup>23</sup>molecules/ 1 mol) = 2.11x10<sup>21</sup>molecules of C<sub>9</sub>H<sub>10</sub>O 3.69 Limestone (CaCO<sub>3</sub>) is decomposed by heating to quicklime (CaO) and carbon dioxide. Calculate how many grams of quicklime can be produced from 1kg of limestone. Answer: CaCO<sub>3</sub> ---> CaO + CO<sub>2</sub> 1kg CaCO<sub>3</sub> x (10<sup>3</sup>g/1kg) x ( 1 mol CaCO<sub>3</sub>/100.09 g CaCO<sub>3</sub>)= 9.91 mol CaCO<sub>3</sub> 9.91 mol CaCO<sub>3</sub> x (1 mol CaO / 1 mol CaCO<sub>3</sub>) x (44.01g of CaO / 1 mol CaO) = 439.66g of CaO 4.17 Write ionic and net ionic equations for the following reactions:

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