44. Solution to Chemistry Problem

Based on the temperatures at which crystallization begins for a two-component system:
1. construct a phase diagram (melting diagram) for system A-B;
2. mark with dots: I—liquid melt containing a % of substance A at temperature T1; II—melt containing a % of substance A, in equilibrium with crystals of the chemical compound; III—a system consisting of solid substance A, in equilibrium with a melt containing b % of substance A; IV—equilibrium of phases of the same composition; V—equilibrium of three phases;
3. determine the composition of a stable chemical compound;
4. determine the qualitative and quantitative compositions of eutectics;
5. plot all types of cooling curves possible for a given system, indicate which compositions on the melting diagram these curves correspond to;
6. in what phase state are systems containing c, d, e % of substance A at temperature T1? What will happen to these systems if they are cooled to temperature T2?
7. Determine the number of phases and the number of conditional thermodynamic degrees of freedom of the system at the eutectic temperature and a molar fraction of component A of 95 and 5%;
8. At what temperature will a melt containing c% of substance A begin to solidify? At what temperature will it solidify completely? What is the composition of the first crystals?
9. At what temperature will a system containing d% of substance A begin to melt? At what temperature will it melt completely? What is the composition of the first drops of melt?
10. Calculate the heats of fusion of substances A and B;
What component and how much of it will crystallize from the system if 2 kg of a melt containing a% of substance A is cooled from T1 to T2? Option No. 4
Systems A – Li2CO3 B – K2CO3
Mole fraction of A, % 0 9 20 33 39.5 44.2
Crystallization onset temperature, K 1133 1055 955 765 773 778
Mole fraction of A, %50 54.5 62 66.6 83.5 100
Crystallization onset temperature, K 788 778 765 798 911 983
Option No. T1, K a b c d e T2, K
4 923 40 75 10 40 86 768