In the theorem of mathematical definition, the condition that explains the restriction must be satisfied, and the condition that has not been explained can be satisfied or not?

In the theorem of mathematical definition, the condition that explains the restriction must be satisfied, and the condition that has not been explained can be satisfied or not?

Yes, if the definition theorem is not omitted

Explain the reason that limestone can't turn into gold with chemical knowledge
The main component of limestone is CaCO3
Gold Au
Explain with the law of conservation of mass

According to the saying in Chemistry: the atom is the smallest ion in the chemical change, and the type of element does not change before and after the chemical reaction
The main component of limestone is calcium carbonate, and gold does not widely exist in limestone,
Therefore, a large number of elements in limestone can not be changed into gold by chemical change

Explain a practice with chemical knowledge······························
1. Mix calcium chloride into mortar to prevent freezing during construction in winter
why?
2. The iron knife is easy to rust after cutting pickles
why?

1: Why is freezing? Because it contains water, and calcium chloride is a water absorbent. Adding calcium chloride into mortar can absorb water and prevent freezing
2: There are many kinds of ions in pickled vegetables, which adsorb on the kitchen knife will produce faster electrolysis reaction and accelerate the rusting of the kitchen knife