Experiment 8 Department of Nebraska Kearney Chemistry The Copper Cycle Chemical

Question

Experiment 8 Department of Nebraska Kearney Chemistry The Copper Cycle Chemical reactions surround us everywhere in nature and in the man-made world. Reactions are used for the synthesis of most substances of use in society including polymers, paints, fabrics, metals medicines, and many others. Reactions inside the body metabolize our food and power our thoughts and motions. Burning of gasoline, a reaction of gasoline with the oxygen in the air, causes our automobiles to move. Without reactions there would be no life or any material world. There are many different types of chemical reactions but three will come into play in this experiment: decomposition, single replacement, and double replacement. Decomposition reactions occur when reactants break down into simpler products, often pure elements. These reactions take the general form of AB A B. The electrolysis of water to form hydrogen and oxygen gases is an example of a decomposition reaction. 2 H20 2 H2 O2 The experiment performed earlier in the semester in which potassium chlorate was heated to release oxygen gas is another example of a decomposition reaction. 2 KCIO 2 KCI 30 Single replacement reactions often involve the reduction and oxidation of metals with the following general formula: A BC AC B. The reaction of copper metal with silver nitrate to form silver metal and copper(II) nitrate is an example of a single replacement reaction. Cu 2 AgNO3 Cu (NO 2 Ag In this case the copper loses electrons and is therefore oxidized while silver gains electrons and is reduced Cu Cu 2 2e' (oxidation) Ag" e" (reduction) Double replacement reactions involve the switching of partners. These reactions have the general formula of AB CD AD CB. Note that for ionic reactions, each cation is paired with the opposite anion. The ldentification of Anions laboratory had several examples of double replacement reactions involving the formation of a solid or a gas from two salt solutions. All th ilver nitrate and barium chloride reactions are double replacement reactions. For example: AgNO3 Naci AgCl NaNO, BaCl2 Na2SO4 BaSO4 2 Naci Many neutralization reactions are also double replacements. In these reactions, aqueous solutions of acids and bases react to form a salt and water. For example, nitric acid and calcium hydroxide react to form water and calcium nitrate. After the reaction of equal equivalents of acid and base the solution is neutral, meaning that it is no longer acidic or basic 2 HNO3 Ca(OH2 Ca(NO3)2 2 H2O Chem 145L Manual- Page 40

Explanation / Answer

Q1.

m = 0.456 g of copper

m recover = 0.413 g

a)

% recovery = actual/ total * 100% = 0.413/0.456 * 100 = 90.570 %

b)

according to the conservation law... the recovery should be 100% since it is not destroyed

Q2.

a)

Copper(II) oxiede -> CuO

b)

Copper(II) chloride --> CuCl2

c)

Nitric acid --> HNO3

d)

Copper(II) hydorxide --> Cu(OH)2

e)

Hydrochloric acid = HCl

f)

Copper(II) nitrate Cu(NO3)

3

a

2KCl --> 2K + Cl2

b

2Na + CdS --> Na2S + Cd

c)

Pb(NO3)2 + 2KCl --> PbCl2 + 2KNO3

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