Fructose‑2,6‑bisphosphate is a regulator of both glycolysis and gluconeogenesis for the phosphofructokinase reaction of glycolysis and the fructose‑1,6‑bisphosphatase reaction of gluconeogenesis. In turn, the concentration of fructose‑2,6‑bisphosphate is regulated by many hormones, second messengers, and enzymes.

2.05 x 10²⁴ molecules

Explanation:

The balanced equation for the chemical reaction is the following:

2 HCl + Mg → MgCl₂ + H₂

According to the equation, 2 moles of HCl are required to react with 1 mol of magnesium (Mg), so the moles of HCl required to react with 1.7 mol Mg are calculated as follows:

moles HCl = 1.7 mol Mg x 2 mol HCl/mol Mg = 3.4 mol HCl

We know that 1 mol of any compound is equal to 6.022 x 10²³ molecular entities, so we convert the moles of HCl to molecules as follows:

molecules HCl = 3.4 mol HCl x 6.022 x 10²³ molecules/1 mol = 2.05 x 10²⁴ molecules