12. Bacteria are grown in a petri dish. One side of the dish is sprayed with an antibiotic. After a week, the number of bacteria
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Answer:
a) 0 J
b) W = nRTln(Vf/Vi)
c) ΔQ = nRTln(Vf/Vi)
d) ΔQ = W
Explanation:
a) To find the change in the internal energy you use the 1st law of thermodynamics:
Q: heat transfer
W: work done by the gas
The gas is compressed isothermally, then, there is no change in the internal energy and you have
ΔU = 0 J
b) The work is done by the gas, not over the gas.
The work is given by the following formula:
n: moles
R: ideal gas constant
T: constant temperature
Vf: final volume
Vi: initial volume
Vf < Vi, then W < 0 and the work is done on the gas
c) The gas has been compressed. Thus, its temperature increases and heat has been transferred to the gas.
The amount of heat is equal to the work done W
d)
The solution of Sulfuric Acid (H2SO4) has the following mole fractions:
- mole fraction (H2SO4)= 0.034
- mole fraction (H2O)= 0.966
To solve this problem the formula and the procedure that we have to use is:
- n = m / MW
- = ∑ AWT
- mole fraction = moles of A component / total moles of solution
- ρ = m /v
Where:
- m = mass
- n = moles
- MW = molecular weight
- AWT = atomic weight
- ρ = density
- v = volume
Information about the problem:
- m solute (H2SO4) = 17.75 g
- v(solution) = 100 ml
- ρ (solution)= 1.094 g/ml
- AWT (H)= 1 g/mol
- AWT (S) = 32 g/mol
- AWT (O)= 16 g/mol
- mole fraction(H2SO4) = ?
- mole fraction(H2O) = ?
We calculate the moles of the H2SO4 and of the H2O from the Pm:
MW = ∑ AWT
MW (H2SO4)= AWT (H) * 2 + AWT (S) + AWT (O) * 4
MW (H2SO4)= (1 g/mol * 2) + (32,064 g/mol) + (16 g/mol * 4)
MW (H2SO4)= 2 g/mol + 32 g/mol + 64 g/mol
MW (H2SO4)= 98 g/mol
MW (H2O)= AWT (H) * 2 + AWT (O)
MW (H2O)= (1 g/mol * 2) + (16 g/mol)
MW (H2O)= 2 g/mol + 16 g/mol
MW (H2O)= 18 g/mol
Having the Pm we calculate the moles of H2SO4:
n = m / MW
n(H2SO4) = m(H2SO4) / MW (H2SO4)
n(H2SO4) = 17.75 g / 98 g/mol
n(H2SO4) = 0.1811 mol
With the density and the volume of the solution we get the mass:
ρ(solution)= m(solution) /v(solution)
m(solution) = v(solution) * ρ(solution)
m(solution) = 100 ml * 1.094 g/ml
m(solution) = 109.4 g
Having the mass of the solution we calculate the mass of the water in the solution:
m(H2O) = m(solution) - m solute (H2SO4)
m(H2O) = 109.4 g - 17.75 g
m(H2O) = 91.65 g
We calculate the moles of H2O:
n = m / MW
n(H2O) = m(H2O) / MW (H2O)
n(H2O) = 91.65 g / 18 g/mol
n(H2O) = 5.092 mol
We calculate the total moles of solution:
total moles of solution = n(H2SO4) + n(H2O)
total moles of solution = 0.1811 mol + 5.092 mol
total moles of solution = 5.2731 mol
With the moles of solution we can calculate the mole fraction of each component:
mole fraction (H2SO4)= moles of (H2SO4) / total moles of solution
mole fraction (H2SO4)= 0.1811 mol / 5.2731 mol
mole fraction (H2SO4)= 0.034
mole fraction (H2O)= moles of (H2O) / total moles of solution
mole fraction (H2O)= 5.092 mol / 5.2731 mol
mole fraction (H2O)= 0.966
<h3>What is a solution?</h3>In chemistry a solution is known as a homogeneous mixture of two or more components called:
- Solvent
- Solute
Learn more about chemical solution at: brainly.com/question/13182946 and brainly.com/question/25326161
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