The table below shows how the pressure of water varies by temperature: Temp., C

Question

The table below shows how the pressure of water varies by temperature:

Temp., C

Vapor pressure of water, mmHg

5.0

6.543

10.0

9.209

15.0

12.79

20.0

17.54

35.0

42.18

50.0

92.15

80.0

355.1

100.0

760.0

When Mg is added to an aqueous solution of excess HCl, the metal reacts to make MgCl2(aq) and H2 gas.
When the reaction is complete, the volume of H2 gas collected at 15 C is 101.0 mL.
The atmospheric pressure is 694 torr.

? ? ? ? The table below shows how the pressure of water varies by temperature: When Mg is added to an aqueous solution of excess HCl, the metal reacts to make MgCl2(aq) and H2 gas. When the reaction is complete, the volume of H2 gas collected at 15 ½C is 101.0 mL. The atmospheric pressure is 694 torr. What is the number of grams of Mg that reacted to produce this volume of H2? ? ? ? ? The gas formed by Mg reacting with HCl(aq) is collected in an apparatus shown.

Explanation / Answer

Given,

Pressure, P=694 torr=0.913 atm

Temperature, T=15 C=288K

Volume, V=101.0 ml=0.101 ltr

Moles of H2 formed=PV/RT=0.913*0.101/0.0821*288=3.9*10-3 mol

Reaction occurring is:

Mg +2HCl =MgCl2 +H2

Thus moles of Mg reacted=Moles of H2 formed=3.9*10-3 mol

Mass of Mg formed=3.9*10-3*24=0.0936 g

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