Final answer:
The Correct option is 3). Formulas in a chemical equation begin with a coefficient, used to balance the equation in accordance with the conservation of mass. Plus signs separate reactants and products, and an arrow shows the reaction direction. Coefficients are omitted when equal to one.
Step-by-step explanation:
The question asks about the beginning of a formula in the context of a chemical equation. In chemistry, all formulas in a chemical equation begin with a coefficient, which is a number indicating how many atoms, molecules, or formula units of the substance are involved. Plus signs (+) are used to separate individual reactant and product formulas, and an arrow (→) indicates the direction of the reaction from reactants to products. Coefficients are essential for balancing chemical equations to ensure that atoms of each element are equal on both sides, adhering to the law of the conservation of mass.
For example, in the combustion of propane, the correct balanced chemical equation is:
C3H8 + 5O2 → 3CO2 + 4H2O
Each formula starts with a coefficient (except when the coefficient is one, as it is typically omitted) to balance the number of atoms of each element on both sides of the equation.