Stoichiometry of Reactions in Solution

General Chemistry • Chemical Reactions

Written by STEM Calculators Team Published October 17, 2025 Updated February 24, 2026

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Stoichiometry of Reactions in Solution

In solution problems, we often know a reactant’s molarity \(M\) and volume \(V\). First convert the volume to liters, then compute moles of that reactant via \( n = M\,V \). Those moles set the reaction scale; the balanced coefficients give the mole ratios to every other species, and finally moles are converted to masses with the molar masses.

Workflow

Balance the chemical equation (do not change subscripts).
Pick a reference reactant present in solution and convert its volume to liters.
Compute moles of the reference: \( n_\text{ref} = M_\text{ref} V_\text{ref} \).
For any species \(B\): \( n_B = n_\text{ref}\,\dfrac{\nu_B}{\nu_\text{ref}} \) (use coefficients \(\nu\)).
Convert to mass: \( m_B = n_B\,M_B \) (with \(M_B\) the molar mass).

Example

Precipitation: \( \mathrm{K_2CrO_4(aq) + 2\,AgNO_3(aq) \to Ag_2CrO_4(s) + 2\,KNO_3(aq)} \)

Given: \(25.00\ \text{mL}\) of \(0.250\ \text{M}\ \mathrm{K_2CrO_4}\). Find the mass of \( \mathrm{Ag_2CrO_4}\).

\begin{aligned} V_{\text{ref}} &= 25.00\ \text{mL}\times \frac{1\ \text{L}}{1000\ \text{mL}} = 0.02500\ \text{L} \\ n_{\text{K}_2\text{CrO}_4} &= M V = 0.250\ \frac{\text{mol}}{\text{L}}\times 0.02500\ \text{L} = 6.25\times 10^{-3}\ \text{mol} \\ n_{\text{Ag}_2\text{CrO}_4} &= n_{\text{ref}}\frac{\nu_{\text{Ag}_2\text{CrO}_4}}{\nu_{\text{ref}}} = 6.25\times 10^{-3}\cdot\frac{1}{1} = 6.25\times 10^{-3}\ \text{mol} \\ m_{\text{Ag}_2\text{CrO}_4} &= n\,M = 6.25\times 10^{-3}\ \text{mol}\times 331.7\ \frac{\text{g}}{\text{mol}} \approx 2.07\ \text{g} \end{aligned}

Frequently Asked Questions

How does the calculator use molarity and volume to start a stoichiometry problem?

It converts the solution volume to liters and computes moles of the reference reactant with n = M x V. Those moles set the reaction scale for all other species.

Why must the chemical equation be balanced before using solution stoichiometry?

Balanced coefficients are the mole ratios between species. Without a balanced equation, the coefficient ratios are wrong and the computed moles and masses will be incorrect.

What equations are used to compute moles and masses of the other species?

For any species B, the calculator uses n_B = n_ref x (nu_B / nu_ref) from the balanced coefficients, then converts to mass with m_B = n_B x M_B. M_B is the molar mass from the chemical formula.

Does this tool support charges, electrons, or redox half-reactions?

No. Charges and electrons are not supported because the calculator is designed for standard chemical equation balancing and stoichiometric scaling by atom conservation.

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