It has been determined that fluoride can prevent the decay of tooth enamel. Historically, tin(II) fluoride was added to toothpaste to help combat tooth decay. Titration analysis was used to determine the concentration of tin(II) fluoride in a NMmple of toothpaste. A 10.0 mL sample of tin(II) fluoride solution was acidified and titrated with 0.0100 mol/L potassium dichromate solution as represented by the following equation.
3Sn2+(aq)+Cr2O2−7(aq)+14H+(aq)→3Sn4+(aq)+2Cr3+(aq)+7H2O(l)
Trial I II III IV Final Volume (mL) 9.39 16.93 23.61 30.32 Initial Volume (mL) 2.85 9.39 16.93 23.61 Volume Used (mL)
a.The moles of Cr2O72-(aq) that reacted, expressed in scientific notation, is a.bc x 10-dmol. The values of a, b, c and d are
b.The concentration of Sn2+(aq), expressed in scientific notation, is a.bc x 10-d mol/L. The values of a, b, c and d are
4 years ago
Answered By Omar G
For A, you are given the concentration of potassium dichromate and you need to find the moles. The concentration is 0.0100mol/L and you need to multiply by the volume in litres to get the number of moles. In order to find the volume, you calculate the volume of potassium dichromate used in each trial by subtracting final volume - initial volume. Then, you would take the average of the trials to get the average volume used. For example, trial 1 :9.39 - 2.85= 6.54ml / 1000 = 0.00654 L.
For B, you need to balance the equation to determine the molar ratio between tin(II)fluoride and potassium dichromate. You are asked to find the concentration. In A, you found the number of moles of potassium dichromate. You can used that and multiply by the molar ratio between the two compounds to find the number of moles of Tin(II). Now, you would just need to divide by the volume of tin which is given to you in the question (10.00ml/1000= 0.01L)