1. Suppose that sodium hydroxide and silver nitrate react in an aqueous solution

Question

1. Suppose that sodium hydroxide and silver nitrate react in an aqueous solution. (a). Write the total ionic equation for this reaction. (b). Identify the spectator ions in this reaction, if there are any. (c.) Does a precipitate form? If so, what is its molecular formula? 2. An unknown volume of water at 18.2 degrees celcius is added to 24.4mL of water at 35.0 degreees celcius. If the final temperature is 23.5 degrees celcius, what was the unknown volume? ( Assume that no heat is lost to the surroundings, the density of water is 1.00g/mL.) 3. The following questions refer to the redox reaction: Cu+ HNO3- Cu(NO3)2 + NO2 +H2O. (a.) Write the oxidation number for each atom in the reaction. (b.) Identify the oxidized and reduced elements. How many electrons did they gain or lose? (c). Write a balanced molecular equation for this reaction. Remember to balance the electrons gained and lost. 4. Suppose you have a 5.0L container that contains oxygen (O2) and an unknown ideal gas. You use a manometer and find that the pressure in the container is 3.0atm.The temperature is 23 degrees celcius. Completed the following steps, using your answers from previous steps as you need them in later ones. (a.) The partial pressure of the oxygen gas is 1.3 atm. What is the partial pressure of the unknown gas? (b.) How many moles of oxygen gas are in the container? (c.) You put the container in the freezer, where the temperature is -18 degrees celcius. What is the new total pressure (of both gases) inside the container? (d.) The container, when filled with both gases, weighs 1037.9g. When it is empty, the container weighs exactly 1kg. Use this and all the other information you have to identify the unknown gas. This involvs a few steps; remember that you have two gases in the container. 5. The equation for the formation of carbon monoxide is C(s) + 1/2 O2(g) - CO(g) with delta Hf = -110.5kJ/mol. (a.) What is the change in enthalpy, delta H, when 5 moles of CO are formed? (b.) You can use carbon monoxide to make carbon dioxide by following the equation 2CO (g) + O2(g). Calculate the enthalpy change of this reaction by combining the equation for the formation of carbon monoxide and an equation you write for the formation of carbon dioxide from its elements. The heat of fomation of CO2 is delta Hf = -393.5kJ/mol. 6. Suppose that potassium hydroxide and copper nitrate react in an aqueous solution. (a.) Does a precipitate form? If so, what is its molecular formula? (b.) Write the molecular equation for this reaction. (c.) Write the net ionic equation for this reaction. 7. The following questions refer to the redox reactions: KClO3 (aq) + HBr(aq) - Br2(l) + H2O(l) + KCl(aq) (a.) Write the oxidation number for each atom in the reaction. (b.) Identify the oxidizing and reducing agents. (c.) Write a balanced molecular equation for this reaction. Remember to balance the electrons gained and lost. 8. 35.0 mL of water at 18.2 degrees celcius is added to 24.4 mL of mercury at 35 degrees celcius. What is the final temperature of the mixture? (Assume that no heat is lost to the surroundings. The density of mercury is 13.534g/mL. 9. A93. L sample of dry air cools from 145 degrees celcius to -22 degrees celcius while the pressure is maintained at 2.85 atm. What is the final volume? 10. Explain what delta Hf is and how it differs from delta Hrxn.

Explanation / Answer

1.)a) 1. Sodium hydroxide + silver nitrate    sodium nitrate + silver hydroxide

NaOH(aq) + AgNO3(aq)  NaNO3(aq) + AgOH(s)

Na=Na++e    OH+e=OH-

Ag=Ag++e   NO3+e=NO3-

b)No

c)Yes. AgOH(s)

The precipitate is brown.

2.)Cp for water=4.186J/gC

Let the unknown volume be x

By conservation of energy

X*Cp*(23.5-18.2)=24.4*Cp*(35-23.5)

X=52.94mL

4.)using PV=nRT

N=0.617mol

a)partial pressure of oxygen=1.3 atm

partial pressure of unknown gas=3-1.3=1.7atm

b)mole fraction of O2=1.3/3=0.43

moles of O2=0.43*0.617=0.267moles

c)using PV=nRT

P=0.67*0.0821*255/5=2.80 atm

d)weight of gases=37.9 g

O2=0.267mol=8.544g

Weight of unknown gas=29.356g

Moles of unknown gas=0.35

Molar mass=82.8g

Gas is Kr krypton

5.)a)C+1/2O2-CO   Hf=-110.5kj/mol

For 5 mol it will be-550kJ

b)2CO+O2-2CO2   Hf=-393.5kJ

eenthalpy change =613kJ

9.)v1=93

T1=418K T2=251K

At costant P

V1/T1=V2/T2

V2=55.84L

10.) For any reaction there is an enthalpy change. The "heat of reaction" is the change in enthalpy for that reaction.

The "heat of formation" of a compound is the enthalpy change for the reaction where the compound is made from the elements in their standard states at 25C and 1 atm.

CH4(g) + O2(g) --> CO2(g) + 2H2O(g) DH = -890.4 kJ
This is the heat of reaction for the combustion of one mole of methane is -890.4 kJ.

C(graphite) + 2H2(g) --> CH4(g) DH = -75 kJ
This is the heat of formation of methane. One mole of CH4 is made from the elements in their standard states.

8.)You can solve this as question no2

6.)a)Yes.CuOH

b) 2KOH(aq) + Cu(NO3)2(aq) ---> 2KNO3(aq) + Cu(OH)2(s)

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