he shell of an egg from a chicken is mostly made of calcium carbonate, lined wit
ID: 818267 • Letter: H
Question
he shell of an egg from a chicken is mostly made of calcium carbonate, lined with a semipermeable membrane. The shell of the egg can be dissolved using acetic acid (vinegar). The gas-evolving reaction is as follows:
CaCO3(s)+2CH3COOH(aq) ----> Ca(CH3COO)2(aq)+H2O(l)+CO2(g)
Suppose you start with two fresh eggs, with the shell already dissolved. You place one egg in a solution of corn syrup (75% by weight sucrose [C12H22O11]; 25% water; density of 1.38g/mL) and the other in table salt solution (0.70 M NaCl). In both cases the egg shrivels, but which one will have the greater volume? Assume the eggs are the same size to start, that all solutions behave identically, and you must provide your answer mathematically and explain. (Note: Assume 25 degrees C).
Explanation / Answer
Purpose:
To observe the selective passing of materials into and out of a membrane, and observe the types of materials that are and are not passed through.
Hypothesis:
The passage of solution through the semipermeable membrane of the egg is facilitated diffusion through transport proteins in the egg membrane.
Prediction:
By this hypothesis, the acetic acid solution will dissolve the calcium carbonate in the egg's outer shell, converting it to bubbles of CO2. The membrane will then allow much passage of vinegar through the membrane to attain equilibrium solute concentration (because the vinegar will be a more concentrated solution than the inside of the egg). There will thus be a gain in egg mass. There will be little net mass change in the glucose solution, but the two solutes (acetic acid and glucose) will even out on each side of the membrane. In the water, there will be a net loss of egg mass, as solutes in the egg pass through the membrane to even the concentration of solutes in the water.
Materials:
1) One chicken egg
2) One small beaker
3) One graduated cylinder
4) 100 mL 5% acetic acid solution
5) 100 mL 50% glucose solution
6) 100 mL distilled water
7) 5" x 5" square of plastic wrap
8) Rubber band
9) Ruler
10) About 30 cm of string
11) Balance scale
Procedure:
1) Measure transverse and longitudinal circumferences of egg using string and ruler.
2) Measure mass of egg using balance scale.
3) Place egg in beaker.
4) Measure 100 mL of acetic acid solution with graduate.
5) Pour into beaker.
6) Cover beaker with square of plastic wrap and secure with rubber band.
7) Store egg for one day in an undisturbed, cool, dry place.
8) Repeat steps 1-2.
9) Repeat steps 3-8 for glucose solution and distilled water.
Observations:
Upon placing the egg in the acetic acid solution, we observed small bubbles rapidly forming around the outside of the egg. When we retrieved the egg one day later, the surface of the solution was foamy, with yellowish film in some places. The egg was soft and the now-powdery outer shell flaked at the touch. Where the egg came in contact with the bottom surface of the beaker, the shell was intact.
Upon placement in the glucose solution, the egg floated relatively high in the solution. When the egg was retrieved one day later, it still was covered with small bubbles. The appearance of the solution had not changed. The egg still was floating somewhat, but not nearly as high as it had been. The outer shell had thinned to an even greater extent, and there was empty space inside the membrane
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