Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A sample of of mercury(II) chloride () is reduced by tin(II) chloride (). First white calomel forms: . Then more tin(II) chloride turns it into grey mercury: . Use for calomel and for mercury. Find the mass of calomel, the mass of tin(II) chloride for the first step, the mass of mercury at the end and the total mass of tin(II) chloride used.
For a redox reaction, , with , and at 298 K, . A reaction goes if is positive. Moles of reactant come from mass divided by molar mass, and the equation gives the ratios.
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Moles. of HgCl.
Step 2. Calomel. Half as many moles: , which weighs .
Step 3. First tin(II) chloride. .
Step 4. Mercury. All the mercury ends as the metal: .
Step 5. Total tin(II) chloride. The second step needs another , so the total is .
Answer: , , and .
Check. The total tin(II) chloride is as many moles as mercury(II) chloride, since each mercury ion takes one electron and each tin(II) gives two.
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