J2026 O LEVEL COMBINED SCIENCE SECTION C| CHEMISTRY SECTION

[00:00:00]All right, it's Nyaki. It's Niyaki Ozone and today we are simply going to revise the June 2026 combined science from the Zimse exam board as you can see on the screen. Right, so we simply going to dissect this paper step by step. And if you're doing Zimse, you need to pay attention with this instruction, the candidates, right? So in our previous tutorials, we did section A, [music] we did section B and today we are simply going to focus with section C, which is the chemistry section. Right? So we're simply going to have our section section C, right? So always remember to subscribe. Always remember to subscribe so that you'll be notified whenever whenever we post. Right? So we're simply going to have uh the maximum revisions in preparation for the examinations.

[00:00:39]Right? [music] So always stay alert and uh always remember to to subscribe.

[00:00:42]Right? So section C requires us to answer any questions. But for the sake of revisions, we are simply going to answer all the questions. Right? [music] So number 10 says a fig 10.1 shows electrolysis of of water. So electrolysis is simply defined as the decomposition of any compound by passing electric current. So we have electrolysis, we have an electrolyte and then we have what you call the electrodes right. So electrolyte is defined as a compound which when in solution in solution or in aquous phase or in molten phase can allow current to pass through it and then at the same time it decomposes. That's what we call the electrolyte. Right? So electrolytes are only ionic compounds and then in aquous or in solution or in molten phase not in the solid [music] in the solid phase you need to take note on that we doesn't have any conduction in the solid phase like the properties the general properties of any compound no conduction in the solid phase why because all the ions are localized in the latice structure right and then we have what we call the electrodes so electrons these are the points where current either enters or leaves the solution right so here we're simply going to have B and A is the electrons then this one the liquid component is electrolyte right so here we're having acidified water right so water is acidified to increase its conductivity [music] right conductivity right so that's why we incre we are simply going to acidify the water right to increase its conductivity because water itself it is a non electrolyte doesn't have the ions to carry the electric current so we simply going to add acid to increase it [music] conductivity right and then here we're having this battery the source right so here this one connected to this negative terminal is obviously going to be our cathode And then this one is going to be our anode. Right? So the cathode is defined in terms of this phrase is red is red and then n and ox. So reduction at the cathode anode for oxidation.

[00:02:28]Right? So here we're having reduction at this one the cathode and then oxidation at the anode. So here we're having acidified water. Right? So we're simply going to have the ions present. We're having the protons and the hydroxide the hydroxide ions. So the protons are simply going to under reduction. they are simply going to gain electron to form the hydrogen gas. So gaining of electrons is what you call the reduction. Right? So reduction is defined in four phases. So you should know the definition of redux. You should know that one of redux. So redux simply going to have reduction [music] into oxidation in the same reaction occurring simultaneously. Right? So here in terms of reduction we can define reduction as the gain of electrons the gain of hydrogen and then the loss of oxygen and then the decrement decrease in the oxidation oxidation number. So this one is the definition of of reduction right and then oxidation is simply defined as the opposite of reduction. So here we're having the gain. So in terms of oxidation we're having the loss. Here we're having the gain. Again in terms of oxidation we're having the loss. Here we're having the loss. In terms of oxidation, we're having the gain of oxygen. Here we're having the decrement.

[00:03:32]In terms of oxidation, we're having the increment in the oxidation number. Are you together? So you should know the definition of redux. You should know the definition of reduction and oxidation.

[00:03:39]You should be able to define [music] these things. Are we together? So here we're having this one is the reaction in the anode. So to balance, we need to have a two and [music] then a two here.

[00:03:46]So the equation is balanced both ionically and atometrically. Are we together? And then in terms of the reaction occurring at the at the anode, we're simply going to have oxidation. So let me clear here so that we can have the reaction at the anode. So we are simply going to have the hydroxide ions these ones. So hydroxides ions are simply going to be oxidized to give oxygen and and water and then we are simply [clears throat] going to balance using electrons right so we having electrons here. So to balance we need to have a four here then a two them then we also need to have a four here to balance the the charges. So this one is the equation the right. So let us simply go to the the questions so that we can have the full understanding of the questions.

[00:04:23]Right. So yeah, we don't mainly focus on the given question trying to clean papers but we want to broad our foundation. We want to broad our understanding so that you can have the full the clear picture of the concept within the given radius right. So here the first part say describe what happens to acidified water when the switch is closed. So when we are to have the switch being closed [music] we are simply going to have the flow or the passing of current. So if we are having the switch being closed, we're simply going to have current passing through the acidified water and then we're simply going to have electrolysis which we said we are having the decomposition of the ionic compound when current is being passed through it. So we having the production of these gases hydrogen and oxygen right so these are the gases we just simply going to have. [music] So here having oxygen at the we're having hydrogen at the gas. So we are simply going to observe the the bubbles. So also you should know the ratio in which these two gases are simply going to be being produced in the ratio of 2 is to1.

[00:05:15]Why? Because from the water molecule we're having two hydrogen atoms per every water molecule together. So here we are simply going to have the production. So here we're having water decomposing to giving hydrogen plus oxygen. Right? So to balance here we're simply going to have a two and then a two there. Right? So this one going to have the volume of hydrogen produced twice to that one of of oxygen all together. You can also use the diagram.

[00:05:39]Let me clear here so that you can easily confirm. We can also use this diagram to have hydrogen to confirm that hydrogen is on the on this electrode which is the cathode. Right? So here we're having this one the volume the liquid component reduced this one on the are not at the higher level. Right? So this one is on the lower level compared to [music] this one. So this simply mean to say we're having the gas occupying this this space by by the downward displacement of gas method. Right? So here we're simply going to have twice. So as you can see you can easily appreciate that this space is twice to that one. Right? So meaning to say here we're having hydrogen produced in large quantities and then it displaces water twice than this oxygen. Right? So here we're having hydrogen and then here we're having oxygen. Are we together? And then let us move on to the next part. So the next part says um state with the reason the name of the electro A. We've already done that. We said A is our is our cathode connected to this negative terminal. name the product formed at B.

[00:06:35]So here at B we're having oxygen gas being produced being produced from the oxidation of the of the hydroxide ion right and then the next part says um write an equation which occurs at the electro A. So this one [music] is the equation at A and then state any two industrial uses of the substance produced at A. So the uses of hydrogen were being examined on the uses of of hydrogen right we're simply going to have hydrogen being used in the harbor process the manufacturing of of ammonia to form marine and then we can also use hydrogen as a clean as a clean fuel and etc right so hydrogen can also be used as a reducing as a reducing agent right in the extraction of some metals right and then the next part says the next part is number it is number 11 right so let me clear here so that we can have number number 11 so number 11 says contact process produces sulfic acid The equation shows the step towards the production of sulfic acid. So this one is where the wall contact process is right. So so we have fully explained these industrial processes in our topical playlist. So you should start by having a topical playlist before having these exam based revisions. Right? So here we're having this sign which is a reversible sign meaning to say the reaction is a reversible reaction. It proceeds in either in either [music] directions. Right? So here we're having the first equation says the meaning of this sign. Then state any two conditions necessary. So we're having a temperature of 150° [music] and then we're simply going to have a pressure of 1 to 2 atms then vanadium oxide as the as the catalyst right and then also be examined on the uses of a catalyst. So a catalyst increases the rate of a chemical reaction. How? By providing an alternative route with a lower activation energy. Activation energy defined as the minimum amount of energy required to start a chemical reaction. Right? And then identify the source of sulfur dioxide. So sulfur dioxide is obtained from the oxidation of sulfur. Right? So we can oxidize sulfur or we can oxidize ion ion pyates right scale we can oxidize ion pyates right [music] and then the next one says um sulfur dioxide can be directly dissolved in water to produce sulfuric acid. how this direct method is absor is not used [music] right so this direct hydration direct absorption by water is avoided why because it produces the films of sulfuric acid which are difficult to to contain right so we're simply going to avoid this one we're simply going to dissolve this sulfatioide into already made concentrated sulfuric acid to form what you call right so having this one sulfioide plus sulfuric acid to have what you call right so this one is the formula of And then olium is then later diluted to give our sulfuric acid. So ool plus water to give 2 moles of sulfuric sulfuric acid. Right? [music] And then we now move on to the next part which says give one use of sulfuric acid can be used as a list can be used in the manufacturing of fertilizers in the car batteries as an explosive in the manufacturing of detergents pharmaceuticals paints and dyes and etc. So these are the uses of sulfuric acid right and then we now proceed the next part. So the next part says define what is meant by the term the afro. So the avocado's number is divided as the number of particles in one mole of a substance. Right? So the number the number of particles in one mole of a substance. Right? So the particles can either be atoms can be molecules [music] or can be can be ions. Right? So the number of these ions in one mole of a substance. Are you together? So this is what you call the avocado constant.

[00:09:56]Right? And then calculate the number of particles in 0.5 moles of magnesium given that the avocado's constant is equal to 6 by 10 23. Right? So here we're having 1= 6 by 10 to the 23.

[00:10:09]Right? Then here we're told that we're going to have 0.5. So 0.5 is simply going to have less. Right? So 0.5 multiplied over 1* 6 by 10 [music] to the 20 23. Right? So we're simply going to have half of this one. We're having 3 by 10 [music] to the 23. Right? So let us clear so that we can move to the next the next part right. So let me clear here so that we can move to the next part. So the next part says [music] define what is meant by the term empirical empirical formula. So empirical formula is defined as the simplest the simplest one number ratio simplest whole number ratio of atoms present in a compound. Right? So the ratio of all numbers right so you need to highlight that it is the simplest one number ratio of atoms present in a compound. Right?

[00:10:52]So and then molecular formula molecular formula it shows the actual the actual atoms number of atoms present in a compound. So this one empirical formula it is a ratio and then molecular formula it shows the actual atoms present in a compound right. So here let me clear here so that you can have the clear picture of the next one. So we're told that 24 g of carbon combined [music] with 4 g of hydrogen in a chemical reaction and then calculate the empirical formula. So we're having carbon and then we're having hydrogen.

[00:11:22]Here we're having 24 and then here we're having four. Then here we're dividing with 12. Here we're dividing with one.

[00:11:28]So we divide with the a from the periodic table. The mass from the periodic table atomic mass from the periodic table. Right? So for carbon is 20 12. Then hydrogen is one. Right? So here we're simply going to have two. And then here we're having four. And then at this stage [music] you simply going to divide with the with the smallest.

[00:11:42]Right? We divide with the smallest. So this one is two. This one is [music] four. So obviously this one is the smallest. So we're dividing with two.

[00:11:48]then we're dividing with two. So here we're having one here we're having two.

[00:11:51]So the ratio is C1 H2 all together. So the first step you divide this number this number this is what you call the abundance. So you divide the abundance with the A and then from there you're simply going to divide with the smallest [music] one and then you are simply going to obtain the the ratio. Are we together? So here we have this one is the empirical formula and then the next one says define explain what is meant by relative molecular mass. So relative molecular mass is the average mass of a molecule measured relative to 1 / 12 mass of a carbon 12 isotope. Right? So here this one is what you call the relative molecular mass. So you should know the definition of a r atomic mass the m relative molecular mass. So ar is mass of an atom. This one it is mass of a molecule. That's the difference [music] between these two are together.

[00:12:34]And then this one we can obtain this one from the periodic table. And then this one we add because it's a molecule we add the a [music] atoms present in that molecule like this one. Right? So calculate the relative molecular mass of ethine. We're given this one as the ethine, right? So ethine is C2 H4. So the A of carbon is 12. How many carbon atoms? We have two. So it's 12 by two. Then that one of hydrogen is one. How many hydrogen atoms? We have four. And then we're still going to add.

[00:12:59]So it's 2 by 12.

[00:13:02]And then this one + 4. And then we're going to have 28 [music] is the relative molecular mass. So relative molecular mass doesn't have any units. Are you together? So this one we simply going to explain that one later when we're dealing with with chemistry.

[00:13:15]Right. So we simply now moving on to the next part which is section section D.

[00:13:19]Right. All right. So this one is our Nyaki online tutotoring as you can see on the screen. So we specialize in sciences. We specialize in sciences. So we have pyramids, chemistry, physics, biology, combined science, mechanics and statistics for both the O levels and the A levels. Right? So we have our standard package, we have our premium package, we have our premium pro max package. Right?

[00:13:40]So these are affordable. We are starting with the standard with a price of $15 for the O levels per subject and then $20 for the A levels. And then we go to the premium. We are simply going to have 25 for the levels and then 30 for the O levels. And then we simply go to the premium pro max where we simply going to have $40 for the O levels and then $50 for the A levels. Right? So here we're simply going to have these offers per per package. Right? So here we're still going to have WhatsApp only and then here we have WhatsApp and Zoom meet Zoom meetings and then here we only have Zoom meetings right so you should message the admin so that you can register using our these our admin our admin numbers right so always remember to message the admin and then this our YouTube channel so that you can subscribe and then this one our Tik Tok is Nyaki ozone and then we have the WhatsApp number the WhatsApp groups right so you should message the admin so that you'll be aided in our WhatsApp in our WhatsApp group so don't hesitate to get to get in touch