Q1) To measure the molecular weight of creatine, a sample solution of 0.1 g/l is prepared. The osmotic pressure of the s
Posted: Mon May 09, 2022 3:30 pm
Q1) To measure the molecular weight of creatine, a sample
solution of 0.1 g/l is prepared. The osmotic pressure of the
solution against pure water is 1.71 kPa at 25 ◦ C. What is the
molecular weight of creatine? What is the water vapor pressure
above such a solution? The vapor pressure of pure water is 3.13
kPa.
Q2) In living cells, the concentration of sodium ions is
kept lower inside the cells than outside. Consider the following
process at body temperature and atmospheric pressure: 1 mol NaCl
(0.05 M inside) → 1 mol NaCl (0.20 M outside) Write an expression
for the change of Gibbs free energy for this process. b Calculate
the Gibbs free energy change by assuming that the activities are
proportional to the molar concentrations.
Q3. A cell membrane at 37 ◦ C is found to be permeable to Ca2+
but not to anions, and analysis shows the inside Ca2+ concentration
to be 0.100 M and the outside concentration to be 0.001 M. a What
potential difference in volts would have to exist across the
membrane for Ca2+ to be in equilibrium in the stated
concentrations? Assume the activity coefficients are equal to 1.
Give the sign of the potential inside with respect to the outside.
b If the measured potential inside is +100 mV with respect to the
outside, what is the minimum reversible work required to transfer 1
mol of Ca2+ from outside to inside?
Q4. The water in freshwater lakes has a lower salt concentration
than the seawater. Consider the oceans to be a 0.5 M NaCl solution
and fresh water to be a 0.005 M MgCl2 solution. For simplicity,
consider the salts to be completely dissociated and the solution to
be sufficiently dilute to justify the application of Van ’t Hoff
equation. a Calculate the osmotic pressure of the ocean water and
of the lake at 25 ◦ C against pure water. b How much free energy is
required to transfer 1 mol of pure water from the ocean to the lake
at 25 ◦ C? c Which solution, the ocean or the lake has the highest
vapor pressure? d The observed water vapor pressure at 100 ◦ C for
0.5 M NaCl is .0984 MPa. What is the activity of water at this
temperature? The vapor pressure of pure water at 100 ◦ C is 0.1000
MPa.
solution of 0.1 g/l is prepared. The osmotic pressure of the
solution against pure water is 1.71 kPa at 25 ◦ C. What is the
molecular weight of creatine? What is the water vapor pressure
above such a solution? The vapor pressure of pure water is 3.13
kPa.
Q2) In living cells, the concentration of sodium ions is
kept lower inside the cells than outside. Consider the following
process at body temperature and atmospheric pressure: 1 mol NaCl
(0.05 M inside) → 1 mol NaCl (0.20 M outside) Write an expression
for the change of Gibbs free energy for this process. b Calculate
the Gibbs free energy change by assuming that the activities are
proportional to the molar concentrations.
Q3. A cell membrane at 37 ◦ C is found to be permeable to Ca2+
but not to anions, and analysis shows the inside Ca2+ concentration
to be 0.100 M and the outside concentration to be 0.001 M. a What
potential difference in volts would have to exist across the
membrane for Ca2+ to be in equilibrium in the stated
concentrations? Assume the activity coefficients are equal to 1.
Give the sign of the potential inside with respect to the outside.
b If the measured potential inside is +100 mV with respect to the
outside, what is the minimum reversible work required to transfer 1
mol of Ca2+ from outside to inside?
Q4. The water in freshwater lakes has a lower salt concentration
than the seawater. Consider the oceans to be a 0.5 M NaCl solution
and fresh water to be a 0.005 M MgCl2 solution. For simplicity,
consider the salts to be completely dissociated and the solution to
be sufficiently dilute to justify the application of Van ’t Hoff
equation. a Calculate the osmotic pressure of the ocean water and
of the lake at 25 ◦ C against pure water. b How much free energy is
required to transfer 1 mol of pure water from the ocean to the lake
at 25 ◦ C? c Which solution, the ocean or the lake has the highest
vapor pressure? d The observed water vapor pressure at 100 ◦ C for
0.5 M NaCl is .0984 MPa. What is the activity of water at this
temperature? The vapor pressure of pure water at 100 ◦ C is 0.1000
MPa.