Someone asked for more detail on making ZnCl2.....

I bet this makes 'em sorry they asked!

** Zn + 2HCl --> ZnCl2 + H2**This balanced equation can be interpreted many ways:

* 1 mol of Zn + 2 mol of HCl --> 1 mol of ZnCl2 + 1 mol of H2 * 10 mol of Zn + 20 mol of HCl --> 10 mol of ZnCl2 + 10 mol of H2

* 6x10^23mol Zn + 12x10^23 HCl --> 6x10^23 ZnCl2 + 6x10^23 H2

* 65.4g Zn + 36.5g HCl --> 136.4g ZnCl2 + 2g H2How many moles of H2 could be produced with 8 moles of HCl?

8 mol HCl x {1 mol H2 / 2 mol HCl} = 4 mol H2

**How many moles of Zn are needed to produce 0.25 mol ZnCl2?**0.25 mol ZnCl2 x {1 mol Zn / 1 mol ZnCl2} = 0.25 mol ZnCl2

A simple way to look at this problem can be used:

grams A --> mols A --> mols B --> grams B

where: A is the substance given in the question, converted to moles using

the atomic/molecular mass.

To convert moles A to moles B, we simply use the mole ratio from the

balanced equation.

B is the substance to be determined, converted to grams by using the

atomic/molecular mass.

**Calculate the no. of grams of Zn required to produce 3 mol of H2 gas.**We first use step 2, the moles of A (3 mol of H2) and convert to moles B

(mol Zn), then we convert moles of B to grams of B (grams of Zn) to get the

final answer.

3 mol H2 x {1 mol Zn / 1 mol H2} x {65.4 g Zn / 1 mol Zn} = 196.2 g Zn

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