How much chalcopyrite had to be mined to produce 100 pennies if reaction 1 had a percent yield of 68.00 % and all other reaction steps had yield of 100%?

Explanation:

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In this case, the set of chemical reactions are shown below:

(1) 2 CuFeS₂ + 3 O₂ ----> 2 CuS + 2 FeO + 2 SO₂

(2) 2 FeO + SiO₂ ----> 2 FeSiO₃

(3) 2 CuS ----> Cu₂S + S

(4) Cu₂S + S + O₂ ----> 2 Cu + 2 SO₂

In such a way, the pennies are assumed to be 100% copper, and each penny has about 3.0 g of copper, so based on the 4th reaction, we compute moles of Cu₂S and pass through until the 1st reaction as shown below:

Now, from the 3rd reaction we compute the moles of CuS:

2nd reaction is needless, so we proceed to compute CuS's theoretical amount since the 4.72 mol of CuS are said to be actually obtained (real amount) as shown below:

Now, we develop the shown-below stoichiometric relationship between CuS and the chalcopyrite to compute the required amount to be mined in grams, for example

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answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

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