The H2 stuff looks ok.
the 24 also confuses me. 1 mole of any gas at STP is 22.4 liters, not 24. I suspect a typo (the missing 2)
13. Solid sodium reacts violently with water, producing heat, hydrogen gas, and sodium hydroxide. How many molecules of hydrogen gas are formed when 48.7 g of sodium are added to water?
2Na + 2H2O = 2NaOH + H2
So far I have this much figured out:
Mass to moles for Na: 48.7g Na x 1mol / 22.990g = 2.118mol Na
...2.118mol Na....(I need help with this part!!)
1.06mol x 6.02*10^23 atoms / 1 mol = 6.38 x 10^23 molecules of hydrogen gas are formed.
That middle part is really throwing me off. I'm seeing people doing this: 2.12/2 x 24 =25.44dm^3 H = 1.06mol
But I really dont understand where the 24 is coming from?? I understand the math behind it, but I'm confused as to how these people are getting that when working through the problem. Thank you!!
8 answers
maybe the H2 is hot when it comes off, so it occupies more space. Do you have some thermal information?
Yeah the question states that when the solid sodium reacts violently with water, it produces /heat/, hydrogen gas, and sodium hydroxide. I never learned anything about how to write heat into an equation, could you explain it to me?
@Steve? Still there, buddy? Can anyone else help me, I'm struggling.
let's do this one step at a time.
1. Write and balance the equation. You've done that.
2Na + 2H2O = 2NaOH + H2
2. Convert g Na to mols. You've done that. 48.7/22.99 = 2.12 mols.
3. Now you want to convert mols Na (what you have)to mols H2(what you want). You do that with the coefficients in the balanced equation.
2.12 mols Na x (1 mol H2/2 mol Na) = 1.06 mols H2 produced.
4. Now you convert mols H2 to molecules. You know that 1 mol of anything contains 6.02E23 of those anythings; therefore, 1.06 mols H2 x (6.02E23 moleculers/1 mol H2) = ?
My notes. There is no need to convert mols H2 to liters before converting to molecules. Doing that brings up that pesky 22.4L(U.S.) or 24 (U.K.). It is worth noting that 1 mole of a gas occupies 22.4 L IF the gas is at STP. At NTP it occupies 24 L which is probably the source of that 24. Unfortunately some people use 20 C as normal T and others like to use 25 C. Finally there is SATP (24.8 L). Also i should note that "normal pressure) is almost always 1 atm in the U. S. but 100 kPa is usually seen in the definitions. The good news in this problem is that none of that matters if you go directly from mols to number of molecules.
1. Write and balance the equation. You've done that.
2Na + 2H2O = 2NaOH + H2
2. Convert g Na to mols. You've done that. 48.7/22.99 = 2.12 mols.
3. Now you want to convert mols Na (what you have)to mols H2(what you want). You do that with the coefficients in the balanced equation.
2.12 mols Na x (1 mol H2/2 mol Na) = 1.06 mols H2 produced.
4. Now you convert mols H2 to molecules. You know that 1 mol of anything contains 6.02E23 of those anythings; therefore, 1.06 mols H2 x (6.02E23 moleculers/1 mol H2) = ?
My notes. There is no need to convert mols H2 to liters before converting to molecules. Doing that brings up that pesky 22.4L(U.S.) or 24 (U.K.). It is worth noting that 1 mole of a gas occupies 22.4 L IF the gas is at STP. At NTP it occupies 24 L which is probably the source of that 24. Unfortunately some people use 20 C as normal T and others like to use 25 C. Finally there is SATP (24.8 L). Also i should note that "normal pressure) is almost always 1 atm in the U. S. but 100 kPa is usually seen in the definitions. The good news in this problem is that none of that matters if you go directly from mols to number of molecules.
Awesome! Thank you so much! My answer was 6.38 x 10^23 molecules
I have the same problem to figure out, but mine gave this equation: Na + H20 -> H2 + NaOH
So I was just wondering what I should do since mine aren't the exact same.
So I was just wondering what I should do since mine aren't the exact same.
Never mind. I figured it out.
1 answer