Posted by Jake on Sunday, September 23, 2007 at 1:08pm.
My objective is to find the molar volume of a gas.
Is this the correct balanced equation for magnesium ribbon reacting with hydrochloric acid to form hydrogen gas?
2Mg (s) + 2HCL (l) ----> H2 (g) + 2MgCl (aq)
Also, I'm required to find the mass of the magnesium ribbon in grams and the moles of the hydrogen gas collected.
Is it correct to multiply the mass per meter (1.702 g/m) by the m of ribbon in order to get the mass?
then once i have the grams do i change it to moles of Mg? how do i get moles of h2? use the mole ratio of the equation?
For Further Reading
AP Chemistry - bobpursley, Sunday, September 23, 2007 at 1:42pm
No. Correct the formula for MgCl2 and then rebalance.
Yes, mass is m/l * length
Yes, then change that mass to moles. You get moles of H2 from the balanced equation coefficents and the moles of Mg.
I will be happy to critique your thinking.
AP Chemistry - Jake, Monday, September 24, 2007 at 6:08pm
Thanks, sir.
This is what I did, could you tell me if its correct?
given value 1.072 g/meter
1.072 g/m X .02 m [the magnesium ribbon was 2.0 cm] = 0.02144 gMg
Then to find the moles of H2:
0.02144 g mg ( 1 mol Mg/24.31 g Mg) (2 mol H2/1 mol Mg) = 1.76 X 10^ -3
all correct except for the moles of H2 per mole of Mg. The coefficents tell me that for each one mole of H2, 2 moles of Mg was consumed.
2Mg (s) + 2HCL (l) ----> H2 (g) + 2MgCl (aq)
To find the molar volume of a gas, you need to determine the volume of the gas at a specific temperature and pressure conditions and then use the ideal gas law equation. The molar volume of a gas is equal to the volume of one mole of the gas.
Now, let's address your question about the balanced equation for the reaction between magnesium ribbon and hydrochloric acid. The correct balanced equation is:
2Mg (s) + 2HCl (aq) --> H2 (g) + 2MgCl2 (aq)
You correctly identified that the formula for magnesium chloride (MgCl2) was incorrect in the initial equation. It should be MgCl2, not MgCl.
Next, let's move on to finding the mass of the magnesium ribbon in grams and the moles of hydrogen gas collected. You mentioned multiplying the mass per meter (1.702 g/m) by the length in meters of the ribbon to get the mass. This is correct. To find the mass of the magnesium ribbon, you can multiply the mass per meter (1.702 g/m) by the length of the ribbon in meters.
In your calculation, you used a length of 2.0 cm, which is 0.02 meters. So, the mass of the magnesium ribbon would be:
mass = (1.702 g/m) * (0.02 m) = 0.03404 g
You correctly obtained the mass of the magnesium ribbon as 0.02144 g. However, there seems to be a discrepancy between the given value of 1.072 g/m and the value you used in your calculation. Please double-check the given value to ensure accuracy.
To find the moles of hydrogen gas (H2) produced, you need to use the mole ratios from the balanced equation. The balanced equation tells us that 2 moles of magnesium (Mg) react to produce 2 moles of hydrogen gas (H2). So, the mole ratio of Mg to H2 is 2:2 (1:1).
Using this mole ratio, you can convert the mass of magnesium to moles of magnesium using its molar mass of 24.31 g/mol:
moles of Mg = (0.02144 g) * (1 mol Mg/24.31 g Mg)
Simplifying the calculation, the moles of Mg is approximately 0.000881 moles.
Since the mole ratio of Mg to H2 is 1:1, the moles of hydrogen gas would also be 0.000881 moles.
It's important to note that the given values and calculations in your response may be incorrect or based on inaccurate information. Please double-check the values and formulas to ensure accuracy in your calculations.