7. When 137.52 g of pure copper reacts with 387.68g of bromine, 483.38g of a gra

Question

7. When 137.52 g of pure copper reacts with 387.68g of bromine, 483.38g of a gray-black compound containing only copper and bromine result. 41.82g of bromine remain when the reaction is complete. a. Do these results support the Law of Conservation of Mass? Explain b. Another student heat 18.14g of copper with 19.89g of bromine. The product is a green-gray compound with mass of 35.71g with 2.32g of copper left over. Is the compound made in this experiment, th e same or different than the first one? If different prove that these two experiments together support the Law of multiple proportions.

Explanation / Answer

The law of conservation of mass states that mass can neither be created nor be destroyed. In a equation the mass of reactants is equal to mass of products.

So the initial mass of reactants is 137.52+387.68=525.2gm

Eventually after reaction gets completed we have mass of bromine left and mass of product which is equal to 41.82+483.38=525.2gm

thus in the equation the mass is conserved as initial mass = final mass.

(b) Law of multiple proportions states that if two elements form more than one compound between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers.

So different products are formed in two reaction, one CuBr and other is CuBr2 so the ratio of masses is 1:2 in compound respectively.

thus, law of multiple proportions is satisfied.

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