A sample of sodium reacts completely with 142 g of chlorine, forming 234 g of sodium chloride. What mass of sodium reacted?

Question

I took 142g of Cl / 35.5g/mol = 4 mols of Cl

Then I took 58.44g/mol x 4 mols of Cl = 233.76

It asked for three significant figures only so I put 233 and 234 but i got the worng answer twice.

Somebody plz help!

Answer 1

Write out your balanced equation for the reaction first.

2Na + Cl2 --> 2NaCl
? 142g 234g

Mols of Cl2
142g / 71 g/mole
= 2 mol of Cl2

Because of the balanced equation, one mol of Cl2 requires 2 mols of Na for all of the chlorine to be used up
... 4 mol of Na

4 mol * 23 g/mol
= 92 g of Na

Answer 2

The other way to do this...

234g sodium chloride - 142g of chlorine = 92g of sodium

Answer 3

NaCl = 23+35.5 = 58.5 g/mol
so 234/58.5 = 4 mols of NaCl

that requires
23 * 4 = 93 grams of Na

Answer 4

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