Notice that "SO4" appears in two different places in this chemical equation. SO42− is a polyatomic ion called "sulfate." What nu

Explanation:

A physical change refers to a modification that does not alter the chemical makeup of a substance.

For instance, characteristics such as shape, size, mass, volume, density, and boiling point are considered physical properties.

Conversely, alterations that result in a change in the chemical structure of a substance are classified as chemical changes.

Examples include combustible substances like dynamite or decomposing cheese, which represent chemical transformations.

Thus, we can conclude that the following are all physical changes in matter:

• boiling water.

• a pencil being sharpened.

• freezing water.

Answer: The vapor pressure of naphthalene within the flask remains at atm.

Explanation:

The transformation from solid naphthalene to its gaseous form follows the equilibrium reaction:

• The formula employed to determine the enthalpy change for the reaction is:  

The formula for calculating the enthalpy change regarding the aforementioned reaction is:

The provided information includes:

Substituting the values into the previous equation produces:

• The formula utilized to compute Gibbs free energy change is of a reaction:

The equation for the enthalpy change for the reaction is:

The given factors include:

By inserting values from the above equation, we arrive at:

• For the calculation of (at 25°C) regarding the provided value of Gibbs free energy, the following relationship is applied:

where,

= Gibbs free energy = 22.5 kJ/mol = 22500 J/mol  (Conversion factor: 1kJ = 1000J)

R = Gas constant =

T = temperature =

= equilibrium constant at 25°C =?

Inserting values into the above equation yields:

• To determine the equilibrium constant at 35°C, we refer to the equation proposed by Arrhenius, which states:

where,

= Equilibrium constant at 35°C =?

= Equilibrium constant at 25°C =

= Enthalpy change of the reaction = 72.1 kJ/mol = 72100 J

R = Gas constant =

= Initial temperature =

= Final temperature =

By plugging values into the equation above, we obtain:

• In order to calculate the partial pressure of naphthalene at 35°C, we utilize the equation for , which is:

The partial pressure of the solid phase is considered to be 1 at equilibrium.

Therefore, the value for will equal

Consequently, the partial pressure of naphthalene at 35°C is atm.

Answer:

Calcium's atomic radius is roughly 175 pm.

Explanation:

We know that magnesium has an atomic radius of 150 pm.

The atomic radius of strontium measures 200 pm.

Since calcium's position is between magnesium and strontium in group 2 of the periodic table, its atomic radius should be roughly averaged between magnesium's and strontium's atomic radii because atomic radius is not constant.

Thus;

Calcium's atomic radius is approximately calculated as follows;

The average atomic radius is (200 + 150)/2 = 175 pm.

Response:

Each molecule consists of one carbon atom.

9.837 * 10^24 molecules correspond to 9.837 * 10^24 carbon atoms.

It's a 1:1 relationship.

Response: Water is a polar substance, facilitating the dissolution of ionic compounds due to the principle that similar types mix.

Ionic interactions occur between salt and water

Sugar contains hydroxyl groups that can form hydrogen bonds with water molecules.

[Hydrogen bond: this refers to the attraction between a hydrogen atom bonded to a highly electronegative atom (like F, O, or N) and another highly electronegative atom (F, O, or N)]

Thus, due to the presence of hydrogen bonds, sugar dissolves in water.

Clarification: Water molecules are polar, exhibiting partial positive charges on the hydrogen atoms and a partial negative charge on the oxygen atom. This allows them to interact with ionic compounds such as salt (NaCl). These interactions occur through the partial charges on water, which attract opposite charges. When dissolved in water, NaCl dissociates into sodium and chloride ions; sodium ions are surrounded by negatively charged oxygen from water, while chloride ions are surrounded by positively charged hydrogens from water. As a result, salt dissolves in water.

Sugar, being a covalent compound, has bonds where electrons are shared unevenly, creating slight positive and negative charges. This characteristic allows sugar to interact with the polar ends of water, facilitating its dissolution. Therefore, it can be stated that sugar dissolves in water due to both substances being polar.

In summary, water is capable of dissolving most polar or ionic substances, as seen with sugar and salt.