Molarity from a pressure problem?
1) A 330mL sample of a HCl solution reacts with excess Mg to produce 4.05L of H2 gas measured at 745 mmHg and 35Celsius.
Mg(s) + 2HCl(aq) -->MgCl2(aq) + H2
What is the molarity of the HCl solution?
Is this a PV=nRT problem? and the n would be the molarity?
The balanced equation for questions 2&3 is: NiCl2(aq) + 2NaOH(aq) ---> Ni(OH)2(s) + 2NaCl(aq)
2) How many milliliters of 0.200M NaOH are needed to react with 28.0mL of 0.500M NiCl2 solution?
I thought this was a M1V1=M2V2 and solved for V2, I got 11.2mL but it said I was wrong.
3) How many grams of Ni(OH)2 are produced from the reaction of 25.0mL of 1.75M NaOH solution?
Not sure how to do this one...
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Verified answer
1)
First, find the number of moles of H2 produced:
PV = nRT
n = PV / RT = (745 mmHg) x (4.05 L) / ((62.36367 L mmHg/K mol) x (35 + 273 K)) =
0.15708 mol H2
Then use the balanced equation to find the number of moles of HCl, then divide by the volume:
Mg + 2 HCl → MgCl2 + H2
(0.15708 mol H2) x (2 mol HCl / 1 mol H2) / (0.330 L) = 0.952 mol/L HCl
2)
NiCl2 + 2 NaOH → Ni(OH)2 + 2 NaCl
(28.0 mL) x (0.500 M NiCl2) x (2 mol NaOH / 1 mol NiCl2) / (0.200 M NaOH) =
140 mL NaOH
3)
(0.0250 L) x (1.75 mol/L NaOH) x (1 mol Ni(OH)2 / 2 mol NaOH) x
(92.70819 g Ni(OH)2/mol) = 2.03 g Ni(OH)2