Ann dissolves four tablespoons of salt in a bowl of water. She notices that the water has become salty. Ann then keeps the bowl out in the Sun for a long time. The water in the bowl evaporates, leaving crystals of salt behind in the bowl. What kinds of change(s) have happened?

Both the salt dissolving and the evaporation of water leaving salt are physical changes.
Both the salt dissolving and the evaporation of water leaving salt are physical changes.

Both the salt dissolving and the evaporation of water leaving salt are chemical changes.
Both the salt dissolving and the evaporation of water leaving salt are chemical changes.

The salt dissolving is a physical change, and the evaporation of water leaving salt is a chemical change.
The salt dissolving is a physical change, and the evaporation of water leaving salt is a chemical change.

The salt dissolving is a chemical change, and the evaporation of water leaving salt is a physical change.

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explanation:

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.