The movement of molecules from an area of low concentration to an area of high concentration occurs in (blank) transport. In (blank) transport, molecules move from an area of high concentration to an area of low concentration.

During active transport, molecules move from an area of low concentration to an area of high concentration. Active transport is called "active" because this type of transport requires energy to move molecules. ATP is the most common source of energy for active transport.

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As Bob add more solute to dissolves, the rate of solution will be decreases

Explanation:

At certain temperature the maximum amount of solute dissolve in the specific amount of solution or solvent.

There are many factors that affect solubility of the solute in solvent. Nature of the solute also affects the rate of solubility.

Temperature also affects the rate of solubility. Solubility increase when the temperature increases.

Pressure: Change in pressure have no effect on the rate of solubility

The rate of solution:  is a measure that how fast a substance dissolves in solvent.

Amount of solute already dissolved affect the rate of solution. If a solvent have little amount of solute in the solution it dissolve quickly. But when you have more solute in the solution the process was slower.

1 g of lead dissolves in 100 g of water at room temperature.  Similarly 5 mg of sodium hydroxide pellet dissolve in 100ml of water at room temperature.

So if Bob add 1 mg more of NaOH in the same 100ml of water the rate of the solubility decreases.

As there are some factors that decrease the solubility rate of NaOH pellet as follow:

•large size of the solute dissolve slowly as the solubility process take on      the surface of the solute particles, powders dissolve fast.

•less amount of solvent with ratio to solute

•saturated solution

So due to all above reasons the rate of the solubility decreases upon adding a little more amount of NaOH pellet.