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HINT: remember that the enthalpy of formation of elements in their standard state is zero. Take the third chemical equation, and write it in reverse. Multiply the first equation times two. Multiply the second equation times three. What do you notice? Can you figure it out?

2013 Q.20 First we have to convert 450 nanometres light to a frequency, and mark this point on the horizontal axis of the graph. 450 nm corresponds to 6.7 x 1014 Hz, which is below the cut-off frequency for metal Y, but above the cut-off frequency for metal X. We are also aware that a change in...

add to your list, you also need to understand conductivity titrations.

In the apparatus shown, the electron flow is from cathode to anode. Therefore the flow of positive charge (conventional current) is from anode to cathode. Apply the "right-hand curl" rule. If your right thumb points in the direction of conventional current, then your fingers curl in the...

TODAY'S CHALLENGE PROBLEM. This should test your understanding of static equilibrium and free-body diagrams. Sorry! No prize for the first correct answer, just the satisfaction from working it out.

Borders are a good idea, but honestly you should leave it to last. First you have to work out how many rows and columns you need and how wide they should be, etc etc so if you have time left over, then, yes put the borders in.

Hmm ... no, this is not part of Physics Module 6. It has a bit to do with the discovery of electromagnetic waves by Heinrich Hertz in 1887, and bit of revision of Physics Module3 'Waves and Thermodynamics". At the free ends of a wire, there cannot be any current (or else where is the current...

Since you are revising for Modules 5 and 6, I will give you a few examples from these modules that will broaden your conceptual thinking, as your teacher suggests. Conceptual exercises start with an inquiry question, something like "If the Earth and the Moon both exert a gravitational force on a...

The intention by NESA is that your depth study must represent 15 hours of in-class time. That's all they say about the length of a depth study. To quote the syllabus, "The length of time for any individual depth study and the pedagogies employed are not prescribed." However, many schools do not...

Question 11. Remember: At the equivalence point, there are still reactants and products in the flask. Don't think that because you have reached the equivalence point that the reaction has gone to completion. No, it hasn't. One of the most important techniques about titraton is to slow down when...

Question 30. Think about the pH function mathematically. It says pH = - log [H] Double the concentration [H] and the pH only changes by - log[2] which is -0.3 pH units. What this means is the pH curve is quite insensitive at the low pH end, so you can't rely on the drawn shape of the pH curve at...

This is how you unpack Question 19 - Step 1. Identify which acids are monoprotic, diprotic or triprotic etc. Step 2. Write the balanced chemical equation for each neutralisation. Step 3. Figure out if there is a limiting reagent, using the standard methods of chemical stoichiometry. Step 4...

I have purchased literally hundreds of different brands of laptops for a dozen different schools, so I have a bit of experience in this area. After considering all the things you mentioned, you should get the HP ProBook X360 435 G9 with AMD Ryzen R5 processor, 13.3 inch touch screen, with 16GB...

It depends on where you draw the line for distinguishing a strong acid from a weak acid. This is a broad distinction. I suppose you could say if pKa < 0 then you are definitely dealing with a strong acid, Then you have something like oxalic acid (ethanedioic acid) which is pKa = 1 it's still...

If you are considering building your own motor, then you might like to watch my Physics video on the motor effect:

You could build a motor. You can see my experimental motor in this video on YouTube:

I think you will find that is a reduction gearbox, and the output speed from the gearbox is extremely low. Conversely, the output torque will be extremely high. The inner workings of the motor are concealed, so you can't really change any variables about the motor. That Tamiya product looks like...

The first thing to note about this question is, it doesn't state what sort of wave we are talking about. However, it is pretty clear this must be an electromagnetic wave, because energy is quantised. For all other sorts of waves, like water waves, waves on strings, sound waves etc. the energy...

OK. There is nothing wrong with delving deeper into coordination Chemistry, if you can spare the time and interest. The really interesting property of metallic coordination complexes for me is understanding why so many of them are intensely coloured. The visible colour suggests that quantum...

Without seeing the first two parts (a) and (b) of the question, I'm guessing the question concerns titration. In planning titration, the pH indicator should be chosen so that the colour transition occurs near the equivalence point for the neutralisation reaction. Methyl orange transition occurs...