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Stoichiometry | Mole to mole | Grams to grams | Mole to grams | Grams to mole | Mole ratio — Transcript

by Najam Academy · 2,279 words · 326 segments · language en · Watch on YouTube

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  1. 0:00basic introduction to Stoichiometry I
  2. 0:03will teach you all the important
  3. 0:04stoichiometric conversions using Matrix
  4. 0:08firstly let me teach you that what is
  5. 0:11stoichiometry well the word strike you
  6. 0:14means element and the word metri means
  7. 0:17measurement so Stoichiometry is the
  8. 0:20calculation of products and reactants
  9. 0:22and a chemical reaction for example
  10. 0:26consider this general chemical reaction
  11. 0:28with the help of Stoichiometry we can
  12. 0:31find the number of moles of reactants
  13. 0:34and the number of moles of products so
  14. 0:37remember that Stoichiometry is the
  15. 0:40calculation of products and reactants
  16. 0:42and a chemical reaction now let me teach
  17. 0:46you the important concept of
  18. 0:47coefficients and a chemical reaction
  19. 0:49which a lot of students are not
  20. 0:51understanding for example consider this
  21. 0:55chemical reaction hydrogen gas react
  22. 0:57with nitrogen gas to form a ammonia NH3
  23. 1:01now I will balance this chemical
  24. 1:03reaction there are two hydrogen atoms in
  25. 1:06the reactants well there are three
  26. 1:09hydrogen atoms in the products I place
  27. 1:12two with products and three with the
  28. 1:14reactants now three n two two is equal
  29. 1:17to 6 atoms 2 into 3 is equal to 6 atoms
  30. 1:22there are two nitrogen atoms and there
  31. 1:25are also two nitrogen atoms so this is
  32. 1:29complete balanced chemical reaction now
  33. 1:32these three with hydrogen gas is known
  34. 1:34as coefficient of hydrogen gas
  35. 1:37secondly this one with nitrogen gas is
  36. 1:40known as coefficient of nitrogen gas
  37. 1:43while these two with NH3 is known as
  38. 1:46coefficient of NH3 here I will teach you
  39. 1:50three different stories of coefficients
  40. 1:53firstly the coefficients represents the
  41. 1:56amount of substances for example this
  42. 2:00three coefficient of hydrogen gas shows
  43. 2:023 moles of hydrogen gas
  44. 2:05one coefficient of nitrogen gas
  45. 2:07represents one mole of nitrogen gas and
  46. 2:10two coefficient of NH3 represents 2
  47. 2:13moles of NH3 secondly coefficients
  48. 2:17represent a ratio of reactants to
  49. 2:19products for example I write hydrogen
  50. 2:23gas ratio to nitrogen gas to NH3 we know
  51. 2:27that the coefficient of hydrogen gas is
  52. 2:303 that of nitrogen gas is 1 and that of
  53. 2:33NH3 is 2. hence this is the ratio of
  54. 2:37reactants to products thirdly
  55. 2:40coefficients represents number of
  56. 2:42molecules let I write three hydrogen gas
  57. 2:46one nitrogen gas two NH3 now this three
  58. 2:50coefficient of hydrogen gas represents
  59. 2:52three molecules of hydrogen gas this one
  60. 2:56coefficient of nitrogen gas represents
  61. 2:59one molecule of nitrogen gas and these
  62. 3:03two coefficient of NH3
  63. 3:05represents two molecules of NH3 just
  64. 3:09remember that Story 1 tells that the
  65. 3:12coefficient represents the number of
  66. 3:14moles Story 2 tells that the coefficient
  67. 3:18represents the ratio of reactants to the
  68. 3:20products Story 3 tells that the
  69. 3:24coefficient represents the number of
  70. 3:25molecules
  71. 3:27now how can we use these stories to
  72. 3:30calculate the amount of reactants and
  73. 3:32products
  74. 3:33well consider this question how can you
  75. 3:37form six molecules of NH3 the answer is
  76. 3:40simple according to the Second Story the
  77. 3:43ratio of hydrogen to nitrogen to NH3 is
  78. 3:46three to one one to two we need 6
  79. 3:50molecules of NH3 I just multiply 2 N to
  80. 3:543 I also multiply the ratio of n 2 by 3
  81. 3:58and that of H2 by 3 now 2 and 2 3 is
  82. 4:03equal to 6 1 into 3 is equal to 3 3 into
  83. 4:073 is equal to 9. this reveals that we
  84. 4:11need 9 molecules of hydrogen gas to
  85. 4:14react with three molecules of nitrogen
  86. 4:16gas in order to form six molecule of NH3
  87. 4:21let me repeat this important statement
  88. 4:23we need 9 molecules of hydrogen gas to
  89. 4:27react with three molecules of nitrogen
  90. 4:30gas in order to form six molecules of
  91. 4:33NH3 to conclude this whole concept any
  92. 4:37coefficient and a reaction shows either
  93. 4:40number of moles a ratio or number of
  94. 4:44molecules and snorted down all these
  95. 4:47important Concepts
  96. 4:49now let me teach you the different
  97. 4:51conversions of Stoichiometry like mold
  98. 4:54to mole conversion consider this problem
  99. 4:56how many moles of nitrogen gas is needed
  100. 5:00to react with 13.5 moles of hydrogen to
  101. 5:03form NH3 well I Write the balanced
  102. 5:07chemical reaction we know that hydrogen
  103. 5:10gas plus nitrogen gas react together to
  104. 5:13form NH3 I put here 3 1 and 2. this is
  105. 5:18the complete balanced chemical reaction
  106. 5:20now according to the given statement
  107. 5:2313.5 moles of hydrogen gas is given we
  108. 5:27need to find the number of moles of
  109. 5:29nitrogen gas although there are several
  110. 5:32ways to calculate it but I will teach
  111. 5:35you my way to calculate such type of
  112. 5:38questions
  113. 5:39firstly I write ratio of hydrogen to the
  114. 5:42ratio of nitrogen gas we know that it is
  115. 5:46three to one now listen carefully we are
  116. 5:49already given the number of moles of
  117. 5:51hydrogen I will write this 13.5 moles
  118. 5:55below the hydrogen gas let me repeat it
  119. 5:59we are already given the number of moles
  120. 6:02of hydrogen gas I will write this 13.5
  121. 6:05moles below this hydrogen gas
  122. 6:09here if three moles of hydrogen gas
  123. 6:12react with one mole then 13.5 moles of
  124. 6:15hydrogen gas react with X moles now I
  125. 6:19will just cross multiply them 3 into X
  126. 6:22is equal to 1 into 13.5
  127. 6:27I divide both sides by 3 after
  128. 6:30calculation I get X is equal to 4.5
  129. 6:34moles this we need 4.5 moles of nitrogen
  130. 6:38to react with 13.5 moles of hydrogen
  131. 6:42hence noted down this important
  132. 6:44conversion
  133. 6:45secondly consider this problem how many
  134. 6:49moles of sulfur trioxide will form when
  135. 6:518.5 moles of sulfur dioxide react with
  136. 6:55oxygen firstly I Write the balanced
  137. 6:58chemical reaction according to the given
  138. 7:01statement sulfur dioxide plus oxygen gas
  139. 7:05react together to form sulfur trioxide
  140. 7:08now two oxygen atoms plus two oxygen
  141. 7:12atoms is equal to four oxygen atoms
  142. 7:15while in the products there are three
  143. 7:18oxygen atoms I place here too and the
  144. 7:22product there are two sulfur atoms in
  145. 7:25the reactant I plus here too hence this
  146. 7:29is the complete balanced chemical
  147. 7:31equation according to the given
  148. 7:34statement
  149. 7:358.4 moles of sulfur dioxide will react
  150. 7:38with oxygen to form X moles of sulfur
  151. 7:41trioxide now I will use my personal way
  152. 7:45to calculate the number of moles of
  153. 7:47sulfur trioxide I established ratio
  154. 7:51between sulfur dioxide and sulfur
  155. 7:53trioxide we can see that it is 2 ratio
  156. 7:56to 2 the number of moles of sulfur
  157. 7:59dioxide is 8.4 moles we need to
  158. 8:03calculate the number of moles of sulfur
  159. 8:05trioxide let it is X now I cross
  160. 8:09multiply them 2 into X is equal to 2
  161. 8:13into 8.4 I divide both sides by 2 after
  162. 8:17calculation I get 8.4 moles thus 8.4
  163. 8:23moles of sulfur dioxide will react with
  164. 8:26excess of oxygen to form 8.4 moles of
  165. 8:30sulfur trioxide hence noted down this
  166. 8:33important problem
  167. 8:35the second type of stoichiometric
  168. 8:37conversion is mole to gram conversion
  169. 8:40for example consider this problem
  170. 8:43firstly I write the complete balanced
  171. 8:47chemical reaction according to the given
  172. 8:49statement propane c3h8 react with oxygen
  173. 8:54to form carbon dioxide plus water it is
  174. 8:58a simple combustion reaction now there
  175. 9:01are three carbons in the reactants and
  176. 9:04one carbon and the products I plus here
  177. 9:073 there are 8 hydrogen in the reactants
  178. 9:10and two hydrogen in the products I place
  179. 9:14here for 2 into 4 is equal to 8 hydrogen
  180. 9:18atoms now 2 and 2 3 is equal to 6 oxygen
  181. 9:22atoms plus four oxygen atoms is equal to
  182. 9:2610 oxygen atoms I write here 5 hence
  183. 9:30this is the complete balanced chemical
  184. 9:32equation now four moles of propane will
  185. 9:35react with oxygen to form X grams of
  186. 9:39carbon dioxide
  187. 9:41Alto there are several ways to calculate
  188. 9:44it but I will use my personal way I
  189. 9:47solve this type of problem in two steps
  190. 9:50in the first step I find the number of
  191. 9:53moles of unknown species like carbon
  192. 9:56dioxide I establish relationship of
  193. 9:59ratio between propane and carbon dioxide
  194. 10:01we can see that it is one two three four
  195. 10:05moles of propane is given and the moles
  196. 10:08of carbon dioxide is unknown I have to
  197. 10:12cross multiply them 1 into X is equal to
  198. 10:154 into 3 after calculation I get X is
  199. 10:21equal to 12 moles of carbon dioxide
  200. 10:24hence four moles of propane will react
  201. 10:26with oxygen to form 12 moles of carbon
  202. 10:30dioxide let me repeat it four moles of
  203. 10:33propane will react with oxygen to form
  204. 10:3612 moles of carbon dioxide
  205. 10:39and the Second Step I just convert the
  206. 10:42number of moles to grams the number of
  207. 10:45moles of carbon dioxide is 12 moles
  208. 10:48which we calculated now the molar mass
  209. 10:51of carbon dioxide is 44 gram to convert
  210. 10:55the number of moles of carbon dioxide to
  211. 10:57grams I use this formula
  212. 11:00number of moles into molar mass we know
  213. 11:03that the number of moles of carbon
  214. 11:05dioxide is 12 moles and two the molar
  215. 11:09mass of carbon dioxide is 44 gram after
  216. 11:12calculation I get
  217. 11:15528 grams of carbon dioxide therefore we
  218. 11:21say that 4 moles of propane will react
  219. 11:23with oxygen to form 528 grams of carbon
  220. 11:28dioxide in such type of problems I
  221. 11:32convert given number of moles to moles
  222. 11:34of unknown species then I convert number
  223. 11:37of moles to grams hence noted down this
  224. 11:40important conversion the third type of
  225. 11:43stoichiometric conversion is grams to
  226. 11:45mole conversion consider this problem
  227. 11:48how many moles of hydrogen are necessary
  228. 11:51to react with 6 gram of nitrogen to
  229. 11:55produce NH3 well as usual I write
  230. 11:59balanced chemical chemical reaction
  231. 12:01hydrogen gas plus nitrogen gas will
  232. 12:04react together to form NH3 I put here 3
  233. 12:081 and 2. this is the complete balanced
  234. 12:12chemical equation
  235. 12:13to solve this type of stoichiometric
  236. 12:16problems I follow two steps in the first
  237. 12:19step I convert the given Mass to mole of
  238. 12:22the known species for example 6 gram of
  239. 12:25nitrogen gas is given and we have to
  240. 12:28find X moles of hydrogen gas we know
  241. 12:31that the given mass of nitrogen gas is 6
  242. 12:34gram and the molar mass of nitrogen gas
  243. 12:37is 28 gram now I will use this formula
  244. 12:40to find the number of moles of nitrogen
  245. 12:43gas given Mass upon molar mass the given
  246. 12:47mass of nitrogen is 6 gram and the molar
  247. 12:50mass of nitrogen gas is 28 gram after
  248. 12:53calculation I get
  249. 12:560.23 moles of nitrogen gas and 6 gram
  250. 13:00are 0.23 moles of nitrogen gas react
  251. 13:03with X mole and the Second Step I will
  252. 13:07find the number of moles of unknown
  253. 13:08species like hydrogen gas I establish
  254. 13:12relationship of ratio 2 between hydrogen
  255. 13:15gas and nitrogen gas it is three to one
  256. 13:19we know that 0.23 moles of nitrogen gas
  257. 13:23react with X moles of hydrogen gas I
  258. 13:26cross multiply them 1 and 2x is equal to
  259. 13:313 and 2 0.23 after calculation I get X
  260. 13:37is equal to 0.69 moles of hydrogen gas
  261. 13:41therefore 6 gram of nitrogen gas will
  262. 13:45react with
  263. 13:460.69 moles of hydrogen gas to produce
  264. 13:50NH3 in such type of problems I convert
  265. 13:54given Mass to number of moles then I
  266. 13:57convert number of moles to number of
  267. 13:58moles of unknown species hence noted
  268. 14:02down this important conversion lastly
  269. 14:05let me teach you grams to grams
  270. 14:07conversion for example consider this
  271. 14:10problem how many grams of oxygen react
  272. 14:14with 10 grams of hydrogen gas to form
  273. 14:17H2O well as usual I write the complete
  274. 14:21balanced chemical equation hydrogen gas
  275. 14:24plus oxygen gas react together to form
  276. 14:27water I write 2 1 and 2. now it is a
  277. 14:31complete balanced chemical reaction here
  278. 14:35the mass of hydrogen gas is given which
  279. 14:38is 10 grams I need to find the mass of
  280. 14:41oxygen gas also I need to find the
  281. 14:44number of moles of hydrogen gas and
  282. 14:46oxygen gas firstly I find the molar mass
  283. 14:50of hydrogen gas oxygen gas and H2O the
  284. 14:54molar mass of hydrogen gas is 2 gram
  285. 14:57that of oxygen gas is 32 gram and that
  286. 15:00of water is 18 Gram now I will follow
  287. 15:03these three steps to solve such type of
  288. 15:06problems in the first step I will find
  289. 15:09number of moles of non-specy like
  290. 15:12hydrogen gas I use this formula number
  291. 15:16of moles of hydrogen gas is equal to
  292. 15:18given Mass upon molar mass the given
  293. 15:22mass of hydrogen gas is 10 gram and its
  294. 15:25molar mass is 2 gram after calculation I
  295. 15:29get 5 moles of hydrogen gas thus 10 gram
  296. 15:32are 5 moles of hydrogen gas react with X
  297. 15:35grams of oxygen and the Second Step I
  298. 15:39find the number of moles of unknown
  299. 15:40species like oxygen gas
  300. 15:43to do so I establish relationship of
  301. 15:46ratio between hydrogen gas and oxygen
  302. 15:49gas we know that it is two to one also
  303. 15:54we know that 5 moles of hydrogen gas
  304. 15:56react with X moles of oxygen gas now I
  305. 16:00cross multiply them 2 into X is equal to
  306. 16:031 into 5. after calculation I get 2.5
  307. 16:08moles hence 5 moles of hydrogen gas
  308. 16:11react with 2.5 moles of oxygen gas now I
  309. 16:15will convert 2.5 moles of oxygen gas to
  310. 16:19grams and the third step I convert the
  311. 16:22number of moles to grams to do so I use
  312. 16:25this formula mass of oxygen gas is equal
  313. 16:29to number of moles and to molar mass the
  314. 16:33number of moles of oxygen gas is 2.5 and
  315. 16:37its molar mass is 32 grams after
  316. 16:40calculation I get 80 grams of oxygen in
  317. 16:44case therefore 10 grams of hydrogen gas
  318. 16:47react with 80 grams of oxygen gas to
  319. 16:51produce H2O in such type of problems
  320. 16:54remember these three steps firstly I
  321. 16:58convert given Mass to number of moles
  322. 17:00secondly I convert number of moles to
  323. 17:04number of moles of unknown species
  324. 17:05thirdly I convert number of moles to
  325. 17:09grams I hope that you have learned all
  326. 17:12about basic stoichiometry

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