Can someone check my answer please:
Magnesium metal(0.100 mol)and a volume of aqueous HCL that contains 0.500 mol are combined to react to completion. how many litres of hydrogen gas (measured at STP) are produced
choices:
4.42
11.1
22.7
2.27
5.53
I like 2.27...
Is this right??
thanks Andy
I don't like any of the answers although 2.27 comes the closest.
Mg + 2HCl ==> H2 + MgCl2.
0.1 mol Mg (Mg is the limiting reagent) will produce 0.1 mol H2 so 0.1 x (22.4 L/mol) = 2.24 L.
I wonder what you have been taught about the molar volume of an ideal gas. I've always used 22.4 L/mol. But your answer implies that 22.7 is being used.
2.27 sounds the best option
It cant be 5.53 or 4.42 the maths don't add up!!!
So i agree thanks
Yes the text book says and I quote:
V=nRT/P=(1.000mol)(8.314kPa L/mol K)(273.15 K)/100kPa=22.71L
This is the molar volume of any ideal gas at STP.(if non-si units of atmospheres and the gas constant value of 0.08206 atm L/mol are used , the value is 22.41 L
Hope that helps...
Andy
On this side of the pond, to use Dr Russ' favorite line, we use 22.4 L/mol. Thanks for the information. The difference is the 100 kPa vs 101.325 (1 atm).
To determine the correct answer, we need to use the balanced chemical equation for the reaction between magnesium metal (Mg) and hydrochloric acid (HCl):
Mg + 2HCl -> MgCl2 + H2
From the equation, we can see that for every 1 mole of Mg, we get 1 mole of H2. Therefore, the number of moles of H2 produced will be equal to the number of moles of Mg used.
In the given problem, we are given the number of moles of Mg as 0.100 mol, so the number of moles of H2 produced will also be 0.100 mol.
Now, we need to use the ideal gas law to convert the number of moles of H2 to volume at STP (Standard Temperature and Pressure).
At STP, 1 mole of any gas occupies 22.7 liters of volume.
Therefore, the volume of H2 gas produced will be:
Volume = Number of moles x Molar volume at STP
Volume = 0.100 mol x 22.7 L/mol
Calculating this, we get:
Volume = 2.27 liters
So, the correct answer is indeed 2.27 liters of hydrogen gas. Well done!