Stoichiometry | Mole to mole | Grams to grams | Mole to grams | Grams to mole | Mole ratio — Transcript
Full transcript
- 0:00basic introduction to Stoichiometry I
- 0:03will teach you all the important
- 0:04stoichiometric conversions using Matrix
- 0:08firstly let me teach you that what is
- 0:11stoichiometry well the word strike you
- 0:14means element and the word metri means
- 0:17measurement so Stoichiometry is the
- 0:20calculation of products and reactants
- 0:22and a chemical reaction for example
- 0:26consider this general chemical reaction
- 0:28with the help of Stoichiometry we can
- 0:31find the number of moles of reactants
- 0:34and the number of moles of products so
- 0:37remember that Stoichiometry is the
- 0:40calculation of products and reactants
- 0:42and a chemical reaction now let me teach
- 0:46you the important concept of
- 0:47coefficients and a chemical reaction
- 0:49which a lot of students are not
- 0:51understanding for example consider this
- 0:55chemical reaction hydrogen gas react
- 0:57with nitrogen gas to form a ammonia NH3
- 1:01now I will balance this chemical
- 1:03reaction there are two hydrogen atoms in
- 1:06the reactants well there are three
- 1:09hydrogen atoms in the products I place
- 1:12two with products and three with the
- 1:14reactants now three n two two is equal
- 1:17to 6 atoms 2 into 3 is equal to 6 atoms
- 1:22there are two nitrogen atoms and there
- 1:25are also two nitrogen atoms so this is
- 1:29complete balanced chemical reaction now
- 1:32these three with hydrogen gas is known
- 1:34as coefficient of hydrogen gas
- 1:37secondly this one with nitrogen gas is
- 1:40known as coefficient of nitrogen gas
- 1:43while these two with NH3 is known as
- 1:46coefficient of NH3 here I will teach you
- 1:50three different stories of coefficients
- 1:53firstly the coefficients represents the
- 1:56amount of substances for example this
- 2:00three coefficient of hydrogen gas shows
- 2:023 moles of hydrogen gas
- 2:05one coefficient of nitrogen gas
- 2:07represents one mole of nitrogen gas and
- 2:10two coefficient of NH3 represents 2
- 2:13moles of NH3 secondly coefficients
- 2:17represent a ratio of reactants to
- 2:19products for example I write hydrogen
- 2:23gas ratio to nitrogen gas to NH3 we know
- 2:27that the coefficient of hydrogen gas is
- 2:303 that of nitrogen gas is 1 and that of
- 2:33NH3 is 2. hence this is the ratio of
- 2:37reactants to products thirdly
- 2:40coefficients represents number of
- 2:42molecules let I write three hydrogen gas
- 2:46one nitrogen gas two NH3 now this three
- 2:50coefficient of hydrogen gas represents
- 2:52three molecules of hydrogen gas this one
- 2:56coefficient of nitrogen gas represents
- 2:59one molecule of nitrogen gas and these
- 3:03two coefficient of NH3
- 3:05represents two molecules of NH3 just
- 3:09remember that Story 1 tells that the
- 3:12coefficient represents the number of
- 3:14moles Story 2 tells that the coefficient
- 3:18represents the ratio of reactants to the
- 3:20products Story 3 tells that the
- 3:24coefficient represents the number of
- 3:25molecules
- 3:27now how can we use these stories to
- 3:30calculate the amount of reactants and
- 3:32products
- 3:33well consider this question how can you
- 3:37form six molecules of NH3 the answer is
- 3:40simple according to the Second Story the
- 3:43ratio of hydrogen to nitrogen to NH3 is
- 3:46three to one one to two we need 6
- 3:50molecules of NH3 I just multiply 2 N to
- 3:543 I also multiply the ratio of n 2 by 3
- 3:58and that of H2 by 3 now 2 and 2 3 is
- 4:03equal to 6 1 into 3 is equal to 3 3 into
- 4:073 is equal to 9. this reveals that we
- 4:11need 9 molecules of hydrogen gas to
- 4:14react with three molecules of nitrogen
- 4:16gas in order to form six molecule of NH3
- 4:21let me repeat this important statement
- 4:23we need 9 molecules of hydrogen gas to
- 4:27react with three molecules of nitrogen
- 4:30gas in order to form six molecules of
- 4:33NH3 to conclude this whole concept any
- 4:37coefficient and a reaction shows either
- 4:40number of moles a ratio or number of
- 4:44molecules and snorted down all these
- 4:47important Concepts
- 4:49now let me teach you the different
- 4:51conversions of Stoichiometry like mold
- 4:54to mole conversion consider this problem
- 4:56how many moles of nitrogen gas is needed
- 5:00to react with 13.5 moles of hydrogen to
- 5:03form NH3 well I Write the balanced
- 5:07chemical reaction we know that hydrogen
- 5:10gas plus nitrogen gas react together to
- 5:13form NH3 I put here 3 1 and 2. this is
- 5:18the complete balanced chemical reaction
- 5:20now according to the given statement
- 5:2313.5 moles of hydrogen gas is given we
- 5:27need to find the number of moles of
- 5:29nitrogen gas although there are several
- 5:32ways to calculate it but I will teach
- 5:35you my way to calculate such type of
- 5:38questions
- 5:39firstly I write ratio of hydrogen to the
- 5:42ratio of nitrogen gas we know that it is
- 5:46three to one now listen carefully we are
- 5:49already given the number of moles of
- 5:51hydrogen I will write this 13.5 moles
- 5:55below the hydrogen gas let me repeat it
- 5:59we are already given the number of moles
- 6:02of hydrogen gas I will write this 13.5
- 6:05moles below this hydrogen gas
- 6:09here if three moles of hydrogen gas
- 6:12react with one mole then 13.5 moles of
- 6:15hydrogen gas react with X moles now I
- 6:19will just cross multiply them 3 into X
- 6:22is equal to 1 into 13.5
- 6:27I divide both sides by 3 after
- 6:30calculation I get X is equal to 4.5
- 6:34moles this we need 4.5 moles of nitrogen
- 6:38to react with 13.5 moles of hydrogen
- 6:42hence noted down this important
- 6:44conversion
- 6:45secondly consider this problem how many
- 6:49moles of sulfur trioxide will form when
- 6:518.5 moles of sulfur dioxide react with
- 6:55oxygen firstly I Write the balanced
- 6:58chemical reaction according to the given
- 7:01statement sulfur dioxide plus oxygen gas
- 7:05react together to form sulfur trioxide
- 7:08now two oxygen atoms plus two oxygen
- 7:12atoms is equal to four oxygen atoms
- 7:15while in the products there are three
- 7:18oxygen atoms I place here too and the
- 7:22product there are two sulfur atoms in
- 7:25the reactant I plus here too hence this
- 7:29is the complete balanced chemical
- 7:31equation according to the given
- 7:34statement
- 7:358.4 moles of sulfur dioxide will react
- 7:38with oxygen to form X moles of sulfur
- 7:41trioxide now I will use my personal way
- 7:45to calculate the number of moles of
- 7:47sulfur trioxide I established ratio
- 7:51between sulfur dioxide and sulfur
- 7:53trioxide we can see that it is 2 ratio
- 7:56to 2 the number of moles of sulfur
- 7:59dioxide is 8.4 moles we need to
- 8:03calculate the number of moles of sulfur
- 8:05trioxide let it is X now I cross
- 8:09multiply them 2 into X is equal to 2
- 8:13into 8.4 I divide both sides by 2 after
- 8:17calculation I get 8.4 moles thus 8.4
- 8:23moles of sulfur dioxide will react with
- 8:26excess of oxygen to form 8.4 moles of
- 8:30sulfur trioxide hence noted down this
- 8:33important problem
- 8:35the second type of stoichiometric
- 8:37conversion is mole to gram conversion
- 8:40for example consider this problem
- 8:43firstly I write the complete balanced
- 8:47chemical reaction according to the given
- 8:49statement propane c3h8 react with oxygen
- 8:54to form carbon dioxide plus water it is
- 8:58a simple combustion reaction now there
- 9:01are three carbons in the reactants and
- 9:04one carbon and the products I plus here
- 9:073 there are 8 hydrogen in the reactants
- 9:10and two hydrogen in the products I place
- 9:14here for 2 into 4 is equal to 8 hydrogen
- 9:18atoms now 2 and 2 3 is equal to 6 oxygen
- 9:22atoms plus four oxygen atoms is equal to
- 9:2610 oxygen atoms I write here 5 hence
- 9:30this is the complete balanced chemical
- 9:32equation now four moles of propane will
- 9:35react with oxygen to form X grams of
- 9:39carbon dioxide
- 9:41Alto there are several ways to calculate
- 9:44it but I will use my personal way I
- 9:47solve this type of problem in two steps
- 9:50in the first step I find the number of
- 9:53moles of unknown species like carbon
- 9:56dioxide I establish relationship of
- 9:59ratio between propane and carbon dioxide
- 10:01we can see that it is one two three four
- 10:05moles of propane is given and the moles
- 10:08of carbon dioxide is unknown I have to
- 10:12cross multiply them 1 into X is equal to
- 10:154 into 3 after calculation I get X is
- 10:21equal to 12 moles of carbon dioxide
- 10:24hence four moles of propane will react
- 10:26with oxygen to form 12 moles of carbon
- 10:30dioxide let me repeat it four moles of
- 10:33propane will react with oxygen to form
- 10:3612 moles of carbon dioxide
- 10:39and the Second Step I just convert the
- 10:42number of moles to grams the number of
- 10:45moles of carbon dioxide is 12 moles
- 10:48which we calculated now the molar mass
- 10:51of carbon dioxide is 44 gram to convert
- 10:55the number of moles of carbon dioxide to
- 10:57grams I use this formula
- 11:00number of moles into molar mass we know
- 11:03that the number of moles of carbon
- 11:05dioxide is 12 moles and two the molar
- 11:09mass of carbon dioxide is 44 gram after
- 11:12calculation I get
- 11:15528 grams of carbon dioxide therefore we
- 11:21say that 4 moles of propane will react
- 11:23with oxygen to form 528 grams of carbon
- 11:28dioxide in such type of problems I
- 11:32convert given number of moles to moles
- 11:34of unknown species then I convert number
- 11:37of moles to grams hence noted down this
- 11:40important conversion the third type of
- 11:43stoichiometric conversion is grams to
- 11:45mole conversion consider this problem
- 11:48how many moles of hydrogen are necessary
- 11:51to react with 6 gram of nitrogen to
- 11:55produce NH3 well as usual I write
- 11:59balanced chemical chemical reaction
- 12:01hydrogen gas plus nitrogen gas will
- 12:04react together to form NH3 I put here 3
- 12:081 and 2. this is the complete balanced
- 12:12chemical equation
- 12:13to solve this type of stoichiometric
- 12:16problems I follow two steps in the first
- 12:19step I convert the given Mass to mole of
- 12:22the known species for example 6 gram of
- 12:25nitrogen gas is given and we have to
- 12:28find X moles of hydrogen gas we know
- 12:31that the given mass of nitrogen gas is 6
- 12:34gram and the molar mass of nitrogen gas
- 12:37is 28 gram now I will use this formula
- 12:40to find the number of moles of nitrogen
- 12:43gas given Mass upon molar mass the given
- 12:47mass of nitrogen is 6 gram and the molar
- 12:50mass of nitrogen gas is 28 gram after
- 12:53calculation I get
- 12:560.23 moles of nitrogen gas and 6 gram
- 13:00are 0.23 moles of nitrogen gas react
- 13:03with X mole and the Second Step I will
- 13:07find the number of moles of unknown
- 13:08species like hydrogen gas I establish
- 13:12relationship of ratio 2 between hydrogen
- 13:15gas and nitrogen gas it is three to one
- 13:19we know that 0.23 moles of nitrogen gas
- 13:23react with X moles of hydrogen gas I
- 13:26cross multiply them 1 and 2x is equal to
- 13:313 and 2 0.23 after calculation I get X
- 13:37is equal to 0.69 moles of hydrogen gas
- 13:41therefore 6 gram of nitrogen gas will
- 13:45react with
- 13:460.69 moles of hydrogen gas to produce
- 13:50NH3 in such type of problems I convert
- 13:54given Mass to number of moles then I
- 13:57convert number of moles to number of
- 13:58moles of unknown species hence noted
- 14:02down this important conversion lastly
- 14:05let me teach you grams to grams
- 14:07conversion for example consider this
- 14:10problem how many grams of oxygen react
- 14:14with 10 grams of hydrogen gas to form
- 14:17H2O well as usual I write the complete
- 14:21balanced chemical equation hydrogen gas
- 14:24plus oxygen gas react together to form
- 14:27water I write 2 1 and 2. now it is a
- 14:31complete balanced chemical reaction here
- 14:35the mass of hydrogen gas is given which
- 14:38is 10 grams I need to find the mass of
- 14:41oxygen gas also I need to find the
- 14:44number of moles of hydrogen gas and
- 14:46oxygen gas firstly I find the molar mass
- 14:50of hydrogen gas oxygen gas and H2O the
- 14:54molar mass of hydrogen gas is 2 gram
- 14:57that of oxygen gas is 32 gram and that
- 15:00of water is 18 Gram now I will follow
- 15:03these three steps to solve such type of
- 15:06problems in the first step I will find
- 15:09number of moles of non-specy like
- 15:12hydrogen gas I use this formula number
- 15:16of moles of hydrogen gas is equal to
- 15:18given Mass upon molar mass the given
- 15:22mass of hydrogen gas is 10 gram and its
- 15:25molar mass is 2 gram after calculation I
- 15:29get 5 moles of hydrogen gas thus 10 gram
- 15:32are 5 moles of hydrogen gas react with X
- 15:35grams of oxygen and the Second Step I
- 15:39find the number of moles of unknown
- 15:40species like oxygen gas
- 15:43to do so I establish relationship of
- 15:46ratio between hydrogen gas and oxygen
- 15:49gas we know that it is two to one also
- 15:54we know that 5 moles of hydrogen gas
- 15:56react with X moles of oxygen gas now I
- 16:00cross multiply them 2 into X is equal to
- 16:031 into 5. after calculation I get 2.5
- 16:08moles hence 5 moles of hydrogen gas
- 16:11react with 2.5 moles of oxygen gas now I
- 16:15will convert 2.5 moles of oxygen gas to
- 16:19grams and the third step I convert the
- 16:22number of moles to grams to do so I use
- 16:25this formula mass of oxygen gas is equal
- 16:29to number of moles and to molar mass the
- 16:33number of moles of oxygen gas is 2.5 and
- 16:37its molar mass is 32 grams after
- 16:40calculation I get 80 grams of oxygen in
- 16:44case therefore 10 grams of hydrogen gas
- 16:47react with 80 grams of oxygen gas to
- 16:51produce H2O in such type of problems
- 16:54remember these three steps firstly I
- 16:58convert given Mass to number of moles
- 17:00secondly I convert number of moles to
- 17:04number of moles of unknown species
- 17:05thirdly I convert number of moles to
- 17:09grams I hope that you have learned all
- 17:12about basic stoichiometry
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