Sodium thiosulfate (Na₂S₂O₃) the major component in photographic fixer solution, reacts with silver bromide to dissolve it according to the following reaction:
AgBr(s) + 2 Na₂S₂O₃(aq) → Na₃Ag(S₂O₃)₂(aq) + NaBr(aq)
b. How many mL of 0.02 M Na₂S₂O₃ contain this number of moles?

Verified step by step guidance

1. Step 1: Start by identifying the number of moles of sodium thiosulfate (Na₂S₂O₃) required. This information should be given or calculated from part (a) of the problem. If not provided, refer to the stoichiometry of the reaction to determine the moles of Na₂S₂O₃ needed.
2. Step 2: Recall the formula for molarity (M), which is defined as the number of moles of solute divided by the volume of solution in liters: $M=\frac{n}{V}$, where $n$ is the number of moles and $V$ is the volume in liters.
3. Step 3: Rearrange the formula to solve for the volume of the solution: $V=\frac{n}{M}$. Here, $V$ is the volume in liters, $n$ is the number of moles of Na₂S₂O₃, and $M$ is the molarity of the solution (0.02 M in this case).
4. Step 4: Substitute the known values into the formula. Use the number of moles of Na₂S₂O₃ from Step 1 and the molarity of 0.02 M to calculate the volume in liters.
5. Step 5: Convert the volume from liters to milliliters by multiplying by 1000, since 1 liter = 1000 milliliters. This will give you the final volume of the 0.02 M Na₂S₂O₃ solution required to contain the given number of moles.

Key Concepts

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It allows us to calculate the amount of substances consumed and produced in a reaction based on balanced chemical equations. Understanding stoichiometry is essential for determining how many moles of a reactant are needed to react with a given amount of another substance.

Molarity

Molarity is a measure of concentration defined as the number of moles of solute per liter of solution. It is expressed in moles per liter (M) and is crucial for calculating how much of a substance is present in a given volume of solution. In this context, knowing the molarity of sodium thiosulfate allows us to determine the volume required to achieve a specific number of moles.

Chemical Reaction

A chemical reaction involves the transformation of reactants into products through the breaking and forming of chemical bonds. The reaction provided shows how sodium thiosulfate interacts with silver bromide to form a complex and sodium bromide. Understanding the specifics of this reaction, including the stoichiometric coefficients, is vital for calculating the amounts of reactants needed.