In a continuous monitoring experiment to investigate the rate of a chemical reaction, a student periodically withdraws a sample of volume Vsample cm3V_{\text{sample}}\text{ cm}^3Vsample cm3 from the reaction mixture, quenches it, and titrates it against a standard solution of concentration Cstd mol dm−3C_{\text{std}}\text{ mol dm}^{-3}Cstd mol dm−3.
Assuming a 1:1 stoichiometric ratio between the reactant in the sample and the titrant, and a titre volume of Vtitre cm3V_{\text{titre}}\text{ cm}^3Vtitre cm3, which of the following expressions correctly calculates the concentration of the reactant (in mol dm−3\text{mol dm}^{-3}mol dm−3) in the sample at that time interval?
Concentration=Cstd×VsampleVtitre\text{Concentration} = \frac{C_{\text{std}} \times V_{\text{sample}}}{V_{\text{titre}}}Concentration=VtitreCstd×Vsample
Concentration=Cstd×Vtitre1000×Vsample\text{Concentration} = \frac{C_{\text{std}} \times V_{\text{titre}}}{1000 \times V_{\text{sample}}}Concentration=1000×VsampleCstd×Vtitre
Concentration=Cstd×VtitreVsample\text{Concentration} = \frac{C_{\text{std}} \times V_{\text{titre}}}{V_{\text{sample}}}Concentration=VsampleCstd×Vtitre
Concentration=1000×Cstd×VtitreVsample\text{Concentration} = \frac{1000 \times C_{\text{std}} \times V_{\text{titre}}}{V_{\text{sample}}}Concentration=Vsample1000×Cstd×Vtitre
91 exam-style questions on OCR GCSE Chemistry Monitoring chemical reactions. Each one has a worked solution and a mark scheme showing where the marks go.