A compound composed of carbon, hydrogen, and chlorine contains...

Question

A compound composed of carbon, hydrogen, and chlorine contains 4.19 x 10²³ hydrogen atoms. If 9.00 g of the compound also contains 55.0% chlorine by mass, what is the empirical formula?

Accepted Answer

here. The practice question states a compound composed of carbon, hydrogen and chlorine contains 4.19 times 10 to the 23 hydrogen atoms. If nine g of the compound also contains 55% chlorine by mass, what is the empirical formula? Now, sometimes you'll run into a question and based on its wording may seem very confusing. But remember just first look to see, what are they asking me to find? They want me to find the empirical formula. Then rely on the steps that you've learned to help calculate the empirical formula. Remember step two, We need to find the masses in grams of each of the elements. So let's do that first. Here we have hydrogen atoms. So what we need to do here is we need to convert those hydrogen atoms into grams. So we have 4.19 times 10 to the 23 hydrogen atoms atoms means we're talking about a single atomic element. So it's just a church by itself. What we're gonna do next is we're gonna go from Adams to moles. Remember that means that we have to use avocados number. So one mole of hydrogen Is 6.02, 2 Times 10 to the 23 hydrogen atoms. And remember I've said this in earlier videos when it comes to working things out like this. If you have something written in scientific notation, it's best to put it in parentheses in your calculator Because based on the model that you're using, you may get an entirely wrong answer. So again, if numbers are written in scientific notation, so a number of times 1020 power put it in parentheses. So now Adams cancel out. We have moles of hydrogen. And we're gonna say that for every one mole of hydrogen it's 1.008g hydrogen. So moles of h cancel out and we have our g as .7013g hydrogen. Alright, so we have hydrogen figured out. Remember this compound is composed of carbon and chlorine as well. They're telling us that our sample ways or compound weighs 9g and 55% of that total mass is chlorine. So we'd say that we have nine g total. We cannot use the percentage form when it comes to math. We have to use the decimal form. So you divide this by 100 and that gives me .55. So it's .55 times nine. So that gives me 4.95 g of chlorine. So now we've found the grams of hydrogen. The grams of chlorine. How do we figure out the grams of carbon? Well, remember we said that our compound weighs nine g. So those nine g are of the carbon, hydrogen and chlorine altogether. We just found out the masses of hydrogen and chlorine. So subtract those from nine and the difference that you have left will have to represent the grams of carbon. So here goes our grams of chlorine plus our grams of hydrogen. So we have left at the end is 3.3487 g of carbon. So this originally difficult looking question is pretty approachable now because we have the grams of each of the elements. So all we're gonna do is follow the steps that we know, we're gonna change those grams into moles, divide them all by the smallest moles and hopefully be able to get our empirical formula at the end. Alright, so we're gonna start out with carbon. So we have those grams of carbon oops. So we have 3.3487 g carbon we have 0.7013 g hydrogen and we have 4.95 g chlorine. I'm writing in this order because that's the order um they're given to us within the question carbon hydrogen and then chlorine. Alright, so one mole of carbon weighs 12.01g. Carbon one mole of H is 1.8 g H. And then one mole of chlorine is 35.45 g chlorine. All the grams will cancel out and we'll have moles at the end. Remember at this point we need to make sure that our moles had at least four decimal places in order to avoid rounding errors. So carbon comes out to be .2788 moles. Carbon Hydrogen comes out to be .6958 moles h. And then chlorine comes out to be .1396 moles of chlorine. Next we divide all the Molds that we've gotten by the smallest mole answer, which would be the .1396. So that would give us one chlorine. And then when we divide hydrogen by that number we get 4.984. And because it's .9 we can round up to five. So that's five h. And then carbon. When we divided by that, we get 1.997 carbon. Again it's .9. So I can round up to two. So we have two carbons, five hydrogen and one chlorine. That means that our empirical formula here would be C two H five cl So again, there will be times when you're gonna run into a question that seems very confusing by the way it's written first, find out what exactly are they asking you to find and then rely on the steps that you've learned to help you get to the answer here. All we have to do is convert all the information we have to the grams of each of the elements. They only give us information on carb on chlorine and hydrogen. We found our grams. We know that the complete mass of the compound was nine g. So we knew that the grams of chlorine and hydrogen. If we subtracted from the nine g, that would give us the mass of the missing carbon. Once you have the grams of everything we follow, the basic steps that we've learned to find our empirical formula. So keep this in mind and remember the best way to approach any question that seems confusing is to first find out what they're asking you to do, and then, if you know any steps, follow those steps as closely as you can to get to your final answer.

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