exchemist

I don't think anyone says dark matter is incomprehensible. In fact there is a fair amount of work going on to enable us to comprehend it. It seems to be an unknown form of matter, but that doesn't make it incomprehensible.

Suppose the trouble with that is that YOU then get death threats, from blokes with beards and MAGA hats!

Could be the latter if the rate of generation of new variants exceeds the ability of vaccines to keep up. We are years from vaccinating the whole population.

I'm not sure about citric acid. With free amines you may get ammonium citrates I suppose, but then you would have got ammonium acetates with vinegar. I've a feeling whatever is creating the odour - and it may not just be amines - may have penetrated into the plastic. Some of these things smell very strong so your nose may detect even traces. (I once had to get rid of an old fridge that had failed 6 months previously, with some frozen shellfish in the freezer compartment! It was in a family holiday house on an island in Brittany, that was not used in the winter months. I had to talk to myself about the chemistry of amines all the time I was cleaning it out, just to avoid gagging.)

Well, actually, checking homework is not my absolute favourite pastime....... This all looks fine to me. You are not doing a reaction with an excess of one of the reactants here, so don't worry about that. I assume from your comments at the end that 2.68 metric tonnes of coal is burnt per person per year in your country. I assume this is the US, as you have had to convert to the old Imperial units at the end - something we gave up in Britain when I was at school in the 1970s. And yes you have one mole of carbon reacting with one mole of diatomic oxygen molecules to make one mole of CO2. My only comment on your working is that you may find it better, soon, to start getting used to standard form (exponential or scientific notation) to express the numbers, to get rid of all these zeros which can become easy to miscount. So 2680kg = 2.68 x 10³ kg = 2.68 x 10⁶ g. But maybe you have not come to that yet. You seem to know what you are doing so have confidence in your other calculations. I expect you have got them right.

Well of course they are not tetrahedra. They have a square base.So like any square pyramid they have 5 sides. A tetrahedron has a triangular base. But this film is worthless. I quote Wikipedia: "The Revelation of the Pyramids (French: La révélation des pyramides) is a conspiracy theory pseudo-scientific documentary directed by Patrice Pooyard and released in 2010."

I suspect some of the hydrocarbon-soluble species, perhaps amines etc., have become adsorbed or even partly dissolved into the plastic material. I've always found this sort of thing very hard to remove. You may have to get a new one. Or you could try leaving it out in the sun for a month or something, to see if sunlight can break down the odour-creating species. But I don't have any suggestions for a quick fix if you have tried both ozone and chlorine based bleaches...unless possibly hydrogen peroxide might help. But I'm just guessing.

I'm not expert on this but don't you need to do some geometry to work out how the path length changes with the off-axis distance of the sound reflector. As the reflector moves in towards the axis and this distance decreases, the difference in path length will decrease so your receiver will encounter successive maxima and minima in the sound, as the direct and reflected beams reinforce or cancel. (The reflected sound will be phase-shifted by π as well, I think.) Unless I've misunderstood the scenario.......

OK, so you maintain they did know π, contrary to what most Egyptologists say. That's fine, I just wasn't clear what you were saying earlier.

Looks OK to me. Just remember the -1 superscript means "per" whatever the unit is. You may find if you rewrite it as a "/" it is easier to see what cancels. And try not to just follow the formula you have been given mechanically, but think what you are trying to do, i.e. the number of moles in a certain volume of solution and then then the number of grams that corresponds to.

I agree it seems a strange* question in some ways but I found this which seems to help: https://www.thoughtco.com/definition-of-conversion-factor-604954 So it says a conversion factor is between different units for the same quantity. In the case of the mole, it is a unit for numbers of particles, expressing them in more convenient form for use in chemistry, so I think I would agree Avogadro's number can be considered a conversion factor. But grams to moles?........ *actually damned silly , in my view. What's the point of tripping students up with pedantry like this, that has no impact on their understanding of physical science? Just puts students off, in my view. But don't tell anyone I said that.

Again you refuse to address the simple case of you jumping in the air. Until you do so, there is no point whatsoever in moving on to more complicated systems that are more challenging to analyse. I suspect @swansont is on the money when he refers to the Gish gallop. You did the same thing on the previous thread. Whenever we got to a position in which you had no option but to understand what we were saying, you switched the subject by introducing a new aspect, to prevent us bottoming it out properly. I don't know whether you do this deliberately, as a form of trolling to wind us all up here for your amusement, or whether it is a psychologically motivated thing you do without being aware of it, because you can't bear to face the fact that your ideas are wrong. You've been at this for around a decade now so I would not be surprised if it is the latter. If you want, you can go your grave believing your have proved Newton wrong, but guess what will be your epitaph. So can we please sort out what happens when you jump in the air, then we can apply that to the vibrating ring and then we can see what is making it move on the table? In that order. Otherwise, I'll assume you are not interested in analysing your experiments properly.

mol/litre x g/mol DOES cancel. And gives you an answer in g/litre. Which actually is OK since you've been asked to work this out for a litre, i.e. on a per litre basis. But in fact, to be pedantic, I asked you to consider how many moles there would be in one litre, the answer to which is "0.025 moles", not "0.025mol/l". So you can plug that into your equation, can't you? You've nearly got this, so don't fall at the last fence. Have confidence!

No dice. I am still trying to get you to be clear about what happens when you jump in the air. So far, you are not managing even that.

OK, so does that mean you recognise your body, when you jump into the air, is not an isolated system? And that, when a system is not isolated, internal forces can cause it to move?

Because, unlike you, we like to get one thing at a time straight, instead of continually lobbing in yet more complicating factors in order to obscure the analysis of the problem.

How can the centre of gravity of your body move, just by the action of internal forces? Haven't you spent the last fortnight telling us Newton's laws say that can't happen?

But it's not an isolated system, that's the point.

When you jump in the air, you use your muscles. There are connected only to your bones, i.e. they act purely internally. How do you account for your ability to jump in the air?

This is now so garbled as to be impossible to tease apart and correct. Almost every word is wrong or meaningless in the context in which it appears. Are you now really now claiming that Newton's laws say the ring can't vibrate, in spite of all the previous explanations?

You are wrong in asserting that " internal forces may not be transferred outside the ring", if the ring is in contact with something external. If you jump up and down on the spot, your muscles exert purely internal forces on the bones of your legs, causing them to extend. If you were not in contact with the ground, nothing would happen. But you are in contact with the ground, so as your legs try to extend they press on the ground and the reactive force from the ground pushes you up. We have already explained why the AC current makes the ring vibrate. What is a vibration? It is a repetitive up and down motion. So exactly analogous to your legs when you jump on the spot. The ring is in contact with the table so every downward motion of the vibration makes the ring jump up in reaction. The motion then changes to an upward one, but the ring is how higher off the table than it was before, so it is free of the table for an instant. There is thus a point in each vibration cycle at which the ring has jumped off the table and is free to move in response to any tiny force. We can get onto that in a minute, but first, do you now understand how a vibrating ring in contact with a table experiences varying forces from it? If you still can't understand this point, we can't move on to the rest of it.

So, let me understand this. The Egyptians, so you say, did not know π, but the pyramids builders who, you say, were Egyptians, did. How does that work? Do you mean that while most of Egyptian society didn't, this hypothetical priestly caste of yours did? Also, you'll have to explain to me why the cutting of the pyramid core into steps precludes them making it 280 cubits high by design.

OK. So, on the right hand side, you know the molar mass. The other thing you need to know is the number of moles of substance, right? How many moles would there be in one litre of the solution, at that concentration?

To put it another way, we know @John2020's (a) is not correct.............because of Newton's laws. @John2020 does not seem to realise they are so well established that the first thing we do in analysing a mechanical system is to apply them and see what they tell us. So the logic is that the ring starts to move, ergo there is an external force responsible. It is then just a matter of identifying how that force arises.

I'm not quite sure what this is about but regarding the effect on g of the Earth's rotation, this once came up elsewhere and I worked out that even at the equator, the reduction in apparent g due to the Earth's rotation was only about 0.3%. It went as follows: - The radius of the Earth is ~4000miles, so its circumference, say at the equator is 2 x π x 4000 which comes to ~25,000miles. - The tangential speed at the equator is therefore 25000miles/day, which is close to 1000mph. - The centripetal acceleration needed to keep an object moving with tangential velocity v, in a circle of radius r, is v²/r. So, for an object at the equator, the apparent centrifugal acceleration it experiences, counter to the acceleration of gravity, will be 1,000,000/4000 = 250 miles/hr². What we need to know is how this acceleration compares with g, the acceleration due to gravity, which is about 10m/sec². To do that, we need to get this result into the same units as g is quoted in:- 1 mile is ~1600m. And 1hr is 3600 seconds. So 250 miles/hr² becomes 250 x 1600/(3600)² = 25 x 16/(360 x 36) = 25 x 4/(360 x 9) = 100/3240 = ~ 0.03 m/sec². So the centrifugal force at the equator, as a proportion of the force of gravity, is of the order of 0.03/10 =0.003, or 0.3%. At higher latitudes it will be less, presumably by a factor of the cosine of the latitude, falling to zero at the poles.