The moving of molecules from areas of high concentration to that of low concentration to gain energy is best described as passive transport
<h3>What is passive transport?</h3>
Passive transport is a type of membrane transport in which chemicals are moved across cell membranes without using energy. Unlike active transport, which uses cellular energy, passive transport uses the second law of thermodynamics to cause the movement of substances across cell membranes.
<h3>Why is passive transport important?</h3>
Passive transport processes are critical to homeostasis. They maintain proper conditions inside the cell and the organism as a whole by letting chemicals to pass into and out of the cell.
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Answer: The number to the left of AC should be 6.
Explanation: The balanced chemical reaction is one in which the number of atoms of each element on the reactant side must be equal to the number of atoms on product side.
The given equation 
is unbalanced as the atoms on the reactant side are not same as number of atoms on product side. This equation is called as skeletal equation.
The balanced chemical equation is :
Thus the number to the left of AC is 6.
