Recent content by Daniel2244

Homework Statement calculate the number of moles of potassium manganate required to neutralise oxalic acid. 2KMn)4- + 5H2C2O42-+ 16H+ --> 2Mn2+ + 10CO2 + H2O Homework Equations n = c x V n= m/Ar The Attempt at a Solution Moles of oxalic acid = 5x10-4 Volumeol of KMnO4 = 0.01085dm-3...

That makes sense. Thanks for the help.

Homework Statement Why is enthalpy of combustion 0KJmol-1 for oxygen? I need to know this for my exam coming up soon. Homework Equations The enthalpy change when 1 mole of a substance is burnt in excess oxygen under standard states under standard conditions. The Attempt at a Solution Oxygen...

When I do it I get:

Yes, I get the same when I use the combustion cycle. ΔH1=-4336, ΔH2=-2326 and ΔH3=-2010 because that cycle gives ΔH2+ΔH3=ΔH1 and -4336. You draw the cycle differently to me, but I get the correct answer when I do it.

My bad, I didn't realize I put ΔHƒ°reaction and ΔHc°reaction. Even when I draw the Hess cycle for formation I still get the equation ΔHreaction = ΣΔHfproducts - ΣΔHfreactants which gives the answer +316kjmol-1 which is incorrect.

The enthalpy of formation equation: ΔHƒ°reaction=∑Δhƒ°(products)-ΣΔHƒ°(reactants) When using the enthalpy of formation equation you get: -2010-((-394x3)+(-286x4))= 316Kjmol-1 However, this answer is wrong. On the mark scheme, the answer is -316Kjmol-1. So I used the enthalpy of combustion...

Thanks for clearing it up for me.

I am unsure about the underlined parts of the cardiac cycle. I was taught that the cardiac cycle started when the blood flowed into the atrium, but wouldn't there be a period when both artia and ventricles are at diastole simultaneously? For the second underlined part I was taught and read that...

Are the following definitions correct? Work done as energy transferred The energy transferred when the forces between two objects interact Work done by a force Work done = force x distance moved in the direction of force applied (W=F*Δs) Work done by a gas Work done = pressure x change...

I don't mean other people can delete other peoples threads, just your own.

I am just curious, why there isn't an option where you can delete your old threads? Is it because someone might have the same question/problem and your threads could provide a solution without a need for them to create a thread?

Homework Statement Describe the principle of operation of reed switch and LDR using wheatstone bridge and potential divider arrangement I can't find any website that says a reed switch uses a wheatstone bridge or potential divider arrangement. The only find I have found it that that a magnet...

So, A thermocouple works by two dissimlar metals being connected at each end. One end is called the hot junction and the other end is a cold junction. When heat is applied to the hot junction, electrons move between the hot junction of the different metals at a faster rate causing the two...

Ok, you've been a great help :)