7&8 please when 15.3 g of sodium nitrate. NaNO_3, was dissolved in water in a ca

Question

7&8 please when 15.3 g of sodium nitrate. NaNO_3, was dissolved in water in a calorimeter. the temperature fell from 25.00 degree C to 2I.56 degree C. If the heat capacity of the solution and the calorimeter is 1071J/ degree C, what is the enthalpy change when I mol of sodium nitrate dissolves in water The solution process is NaNQ_3 (S) right arrow Na^+ (aq) + NO_3^-(aq): delta H = A 10.0 L flask contains 1.031 g O_2 and 0.572 g C0_2 at 18 degree C. What arr the partial pressures of oxygen and carbon dioxide What is the total pressure What is the mole fraction of oxygen in the mixture

Explanation / Answer

Q. 7

Here we are given mass of sodium nitrate and from that we can get its moles. By using the heat capacity of the solution and calorimeter we can get actual heat that we get from reaction. Then we find delta H for the reaction .

Number of moles of sodium nitrate = Mass in g / molar mass

= 15.3 g x 1 mol / 84.9947 g

= 0.180 mol

Calculation of heat of solution.

Heat of solution and calorimeter = Ccal x delta T

Here C cal is the heat capacity of the calorimeter including water., Delta T is the change in T .

q = 1071 J / 0C x ( 21.56 – 25.00 )0c

= -3684.24 J

Now we calculated delta H

Delta H of the reaction = - qcal / n

= 3684.24 J / 0.18 mol

= 20466.7 J / mol

8 )

Calculation of moles
mol = mass in g / molar mass

n CO2 = 0.572 g x 1 mol / 44.01g

= 0.012997 mol

n O2 = 1.031 g x 1 mol / 31.998 g

= 0.032221 mol

Calculation of mole fraction

Mol fraction of CO2 = mol of CO2 / total moles

Mol fraction of O2 = 1 – mol fraction of C

Mol fraction of CO2 = 0.012997/(0.003221+ 0.012997)

= 0.2874

Mol fraction of O2 = 1- 0.2874 = 0.71257

Calculation of total pressure

Total pressure p = nRT/ V

Here p is in atm , R = 0.08206 L atm / K mol

V is 10.0 L

n is total number of moles

p = 0.045218 x 0.08206 x (18.0+273.15 )/ 10.0

= 0.108033 atm

So the total pressure = 0.108033 atm

Now partial pressure

Partial pressure = mole fraction total pressure

Partial pressure of O2 = 0.71257 x 0.108033 = 0.07698 atm

Partial pressure of CO2 = 0.287432*0.108033 = 0.031052 atm

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