Understanding Moles of Hydrogen Gas from Electrolysis

When 482,500 coulombs are passed through water, how many moles of hydrogen gas are formed?

• A. 1.25 mol
• B. 2.5 mol
• C. 5 mol
• D. 10 mol

Answer: (B)

To determine how many moles of hydrogen gas are produced when a specific amount of electric charge is passed through water, one must use Faraday's laws of electrolysis. When water undergoes electrolysis, it splits into hydrogen and oxygen gases. The reaction can be summarized by the half-reaction for hydrogen: \[ 2H^+ + 2e^- \rightarrow H_2(g) \] This equation shows that 2 moles of electrons are required to produce 1 mole of hydrogen gas. To relate the charge in coulombs to moles of electrons, Faraday's constant, which is approximately 96485 coulombs per mole of electrons, comes into play. This constant indicates that 96485 coulombs are needed to transfer one mole of electrons. Given that 482,500 coulombs are passed through water, we can first find out how many moles of electrons this represents: \[ \text{Moles of electrons} = \frac{\text{Total charge}}{\text{Faraday's constant}} = \frac{482,500 \text{ C}}{96485 \text{ C/mol}} \approx 5 \text{ mol} \] Since two moles of electrons are required

Want to Know How Much Hydrogen Gas You Can Get from Water?

When you think about making hydrogen gas from water, doesn’t it feel like you're conjuring something magical? You pass a current through water, and voilà—gas bubbles rise! But how much hydrogen can you actually get? Let’s break it down with chemistry that’s easier than you think.

What’s the Scoop on Electrolysis?

So, picture this: you’ve got water (H₂O), and you decide to run an electric current through it. This process is called electrolysis. During electrolysis, water splits into its basic components—hydrogen and oxygen. This is where chemistry gets exciting! The half-equation for hydrogen looks like this:

[ 2H^+ + 2e^- \rightarrow H_2(g) ]

Breaking Down the Equation

In this equation, two moles of electrons (the tiny things that carry charge) produce one mole of hydrogen gas. Easy enough, right? So if you know how much charge you're pushing through the water, you can figure out how many moles of hydrogen will bubble up to the surface.

Time for Some Math: Coulombs to Moles

Here’s where Faraday’s law comes in to save the day! To relate coulombs (the unit of electric charge) to moles of electrons, we use Faraday's constant, which is about 96,485 coulombs per mole of electrons. This means you need 96,485 coulombs to get a single mole of electrons.

You started with 482,500 coulombs. To find out how many moles of electrons that equals, we’ll do a quick calculation:

[ \text{Moles of electrons} = \frac{482,500 \text{ C}}{96,485 \text{ C/mol}} \approx 5 \text{ mol} ]

Can you believe it? That’s about five moles of electrons swirling around in there!

Back to Hydrogen: How Many Moles Are We Getting?

Since we know that two moles of electrons are required to produce one mole of hydrogen gas, we can find out how many moles of hydrogen are formed.

We take our 5 moles of electrons and divide that by 2:

[ \text{Moles of H}_2 = \frac{5 \text{ mol electrons}}{2} = 2.5 \text{ mol H}_2 ]

Boom! There you have it, folks. When you pass 482,500 coulombs through water, you’re able to yield 2.5 moles of hydrogen gas!

Why Does This Matter?

You might be wondering why understanding this reaction is important, especially for something like the IGCSE Chemistry exam. First off, electrolysis is a key concept in both chemistry and physics. Plus, you’ll encounter it when studying topics like energy sources and environmental chemistry. Knowing how to calculate moles from electric charge adds a big feather to your scientific cap.

And let’s be real—hydrogen as a potential clean fuel source? That’s pretty exciting stuff!

Final Thoughts

As you tackle your studies for the IGCSE exams, remember that chemistry isn’t just numbers and reactions; it’s about connecting these principles to real-world applications. So, next time you run electrolytic experiments or do calculations, think about how this knowledge could lead to innovations in energy.

Stay curious, keep questioning, and who knows? You might just uncover the next big thing in clean energy! Happy studying!