3. Is the following problem correctly solved? If not, identify the error and cor

Question

3. Is the following problem correctly solved? If not, identify the error and correct it. The percent yield of a reaction between elemental zinc and an aqueous solution of 0.50 M hydro- chloric acid is known to be 78.0%. We need to produce 355 g of zinc chloride, what is the minimum amount in mL. of hydrochloric acid that are required, given that zinc is in excess? Zn(s) + 2HCl(aq) - ZnCl2(aq) + H,( X × 0.780 = 35.50 g ZaC, thus X = 45.5 g Zna2 theoretically 45.5 g ZnCL × 1 mole ZnCL / 136286 g × 2 mole HCl/l mole ZnCL × 1 L/0.50 molex 1000 m, 1 L = 1340 mL HCl

Explanation / Answer

When solving this kind of problems you should change the mass of the materials to moles, the statement says we want to to get 35.5 grams of ZnCl2, change this to moles (molar mass of ZnCl2 = 136.28 g/gmol)

n = mass / molar mass, where n is the number of moles

n = 35.5 / 136.28 = 0.26 moles

This is the product after a conversion of 78% so we want to know how many moles are 100% so, from the reaction we know that 1 mole of Zn produces 1 mole of ZnCl2

X * 0.78 = 0.26

x = 0.26 / 0.78 = 0.334 moles of Zn are required

Now find the moles of HCl needed, from the reaction we know that 1 mole of Zn requires 2 moles of HCl so

moles of HCl = 0.334 * 2 = 0.6679 moles of HCl required to find the volume remember that

Molarity is

M = moles / Volume, where M is the molarity

Molarity * Volume = moles

Volume = moles / Molarity = 0.6679 / 0.5 = 1.336 Liters or 1336 ml we can round this value to 1340 ml

The method that you have is very similar the only difference is that it calculates the 100% of yield according to the mass of ZnCl2 and then change it to moles anyway the process is essentially the same so it is correct.

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.