To identify the coefficient in the chemical formula provided, we need to understand what a coefficient is in the context of a chemical equation.
A chemical equation typically includes:
- Reactants: Substances that begin the reaction.
- Products: Substances that are produced as a result of the reaction.
- Coefficients: Numbers placed before the chemical formulas to indicate the proportions of the molecules or compounds involved in the reaction.
In the chemical formula:
[tex]\[ -7 \ Tl_2(SO_4)_3 \][/tex]
\-7 is the number placed before the compound \( Tl_2(SO_4)_3 \). This number tells us how many units of \( Tl_2(SO_4)_3 \) are involved in the reaction.
Let's analyze the options:
1. 2: This number is part of the subscript in the compound \( Tl_2(SO_4)_3 \) and indicates that there are 2 atoms of Thallium (Tl) in each molecule of the compound.
2. 3: This number is part of the subscript inside the parentheses in the compound \( Tl_2(SO_4)_3 \) and indicates that there are 3 sulfate groups \( (SO_4) \).
3. 4: This number is part of the subscript in the sulfate ion \( SO_4 \) and indicates that each sulfate ion contains 4 oxygen atoms.
4. 7: This number is placed before the compound \( Tl_2(SO_4)_3 \) and indicates that there are 7 units of the entire compound involved.
Therefore, the coefficient in the chemical reaction is:
[tex]\[ \boxed{7} \][/tex]
