1) A piece of potassium metal is added to water in a beaker. The reaction that t

Question

1) A piece of potassium metal is added to water in a beaker. The reaction that takes place is 2K(s) + 2H2O(l) ?2 KOH(aq) + H2(g) Predict the signs of w, q, ?U, and ?H.


2) At 373.15K and 1 atm, the molar volume of liquid water and steam are 1.88?10^-5 m^3 and 3.06?10^-2m^3 , respectively. Given that the heat of vaporization of water is 40.79 kJ/mol, calculate the values of ?Hand ?U for 1 mole in the following process: H2O(l, 373.15K, 1 atm) ?H2O(g, 373.15K, 1 atm) 1) A piece of potassium metal is added to water in a beaker. The reaction that takes place is 2K(s) + 2H2O(l) ?2 KOH(aq) + H2(g) Predict the signs of w, q, ?U, and ?H.


2) At 373.15K and 1 atm, the molar volume of liquid water and steam are 1.88?10^-5 m^3 and 3.06?10^-2m^3 , respectively. Given that the heat of vaporization of water is 40.79 kJ/mol, calculate the values of ?Hand ?U for 1 mole in the following process: H2O(l, 373.15K, 1 atm) ?H2O(g, 373.15K, 1 atm)

Explanation / Answer

1) A piece of potassium metal is added to water in a beaker. The reaction that takes place is

2K(s) + 2H2O(l) ?2 KOH(aq) + H2(g)

Predict the signs of w, q, ?U, and ?H.

w = -P*dV, since dV is positive, i.e. H2 gas expands the system, w = negative

q = this is exothermic, since K metal + water releases heat, so Q = positive

U = internal energy of system must decrease, since it is losing plenty of energy (negative)

H = Enthalpy of system must decrease, since it is losing plenty of energy(negative)

2) At 373.15K and 1 atm, the molar volume of liquid water and steam are 1.88?10^-5 m^3 and 3.06?10^-2m^3, respectively.

Given that the heat of vaporization of water is 40.79 kJ/mol, calculate the values of ?Hand ?U for 1 mole in the following process:

H2O(l, 373.15K, 1 atm) ?H2O(g, 373.15K, 1 atm)

a) Enthalpy change:

dH = 40.79 kJ/mol

b)

dU = dH - PdV

P = 101325 Pa

Vf = (3.06*10^-2)-(1.88*10^-5) = 0.0305812 m3

P*dV = 101325*0.0305812 = 3098.64 J = 3.098 kJ

dU = 40.79 - 3.098

dU = 37.692 J/mol

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.