chemistry

Chemistry 310

Laboratory Exercise#5

Double Displacement Reactions

Your Name:	Date:

Purpose: To observe a series of double displacement reactions to gain an understanding of the driving forces for these reactions. To learn how to write net ionic equations for a reaction which show the “real” chemical reaction.

Discussion: There is a class of reactions called displacement reactions wherein a component (usually an ion) of a compound is displaced by another reactant.

Double displacement reactions, also called “double replacement” or "exchange reactions”, are very common displacement reactions. Generally, they occur when ionic compounds are dissolved in aqueous (water) solution. The cation of one compound displaces (or swaps places with) the cation of the other compound. They have the general form:

AX + BY AY + BX

where A and B are cations and X and Y are anions.

An example is:

Molecular equation:

Na2S( aq) + Co(NO3)2( aq) 2 NaNO3( aq) + CoS( s)

A double displacement reaction will take place if one or more of the following products is formed:

(a) a precipitate (what you see is a solid material that clouds the solution).

(b) a molecular substance

1. water (you will feel the test tube get warm as heat is given off by the reaction)

2. gas (you see lots of bubbles coming out of solution).

These are known as the Driving Force of the reaction - in other words, they “force” the reaction to proceed. If the reaction produces neither a precipitate, nor a gas, nor a molecular substance, then no reaction has taken place. In that case, all of the original compounds or ions still exist unchanged.

In this experiment you will observe 11 different possible double displacement reactions, determine the possible products of the reaction, and write the balanced molecular equation for each reaction.

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Chem 310

Lab Exercise #5 – Double Displacement Reactions

5.1

Step 1: Access the links, watch video of chemical reactions, record your observations in Table 1.

Equation 1: For the first reaction, NaCl(aq) + AgNO3(aq) see https://www.youtube.com/watch?v=ky0zq_GzwWU

Equation 2: For the second reaction, NaNO3 (aq) + KCl(aq) see https://www.youtube.com/watch?v=6aC8vfIgI2Q

Equations 3: For the reaction, Na2CO3(aq) + HCl(aq) see https://www.youtube.com/watch?v=HY2xAafp-wc

Equation 4 For the reaction, NaOH(aq) + HCl(aq) see https://www.youtube.com/watch?v=WI4DizOtu_U

Equation 5: For the reaction, BaCl2(aq) + H2SO4(aq) see https://www.youtube.com/watch?v=VFe36O951ao

Equation 6: For the reaction, copper (II) carbonate (s) + sulfuric acid (aq) see https://www.youtube.com/watch?v=65taHAKiPyo

Equation 7: For the reaction, CuSO4(aq) + BaCl2(aq) see https://www.youtube.com/watch?v=3VMFJ7x1pk0

Equation 8: For the reaction, sodium carbonate and calcium chloride see https://www.youtube.com/watch?v=kKNp0HVgmjI

Equation 9: For the reaction, Iron (III) chloride with ammonium hydroxide see https://www.youtube.com/watch?v=zLLodFXlqOE

Equation 10: For the reaction, NaOH(aq)+ HNO3(aq) see https://www.youtube.com/watch?v=gW-tm7kiaW0

Equation 11: For the reaction, copper (II) sulfate (aq) and potassium iodide (aq) see https://www.youtube.com/watch?v=SG-lygFJjnw

Note: Record your observations in the table given below. Give all pertinent observations such as color changes (state the colors), formation of a precipitate, gas bubbles, heat evolved, etc., or write "no noticeable change."

Data Sheets

Table 1: Observations of double replacement reaction: Please be descriptive.

Equation	Observations
1
2
3
4
5
6
7
8
9
10
11

Writing, Balancing, and Analyzing the Chemical Reactions

In the table below, complete and balance the chemical equation. Indicate all precipitates with an (s) [such as AgCl( s)] and all gases with (g) [such as CO2( g)].

When H2CO3 is formed it decomposes: H2CO3(aq) → H2O(l) + CO2(g). The same is true for H2SO3(aq) → H2O(l) + SO2↑. Here, the ↑ arrow is used instead of (g): both mean that the substance is a gas.

Table 2. Equations for Double Replacement Reactions:

(Please write and balance the molecular equations)

Equations

1. Molecular equation:

Balanced molecular equation:

2. Molecular equation:

Balanced molecular equation:

3. Molecular equation:

Balanced molecular equation:

4. Molecular equation:

Balanced molecular equation:

5. Molecular equation:

Balanced molecular equation:

6. Molecular equation:

Net ionic equation:

Balanced molecular equation:

7. Molecular equation:

Balanced molecular equation:

8. Molecular equation:

Balanced molecular equation:

9. Molecular equation:

Balanced molecular equation:

10. Molecular equation:

Balanced molecular equation:

11. Molecular equation:

Balanced molecular equation:

What did you learn from this experiment?

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