An aqueous solution of methylamine CH3NH2 has a pH of 10.56 . How many grams of methylamine are there in 100.0mL of the solution? Round your answer to 2 significant digits.<\/p>\n\n\n\n
The correct answer and explanation is:<\/mark><\/strong><\/p>\n\n\n\n To find the amount of methylamine (CH\u2083NH\u2082) in the solution, we must first determine the concentration of methylamine and then convert it to mass.<\/p>\n\n\n\n Given that the pH of the solution is 10.56, we can find the pOH of the solution by using the relationship: pOH=14\u2212pHpOH = 14 – pH pOH=14\u221210.56=3.44pOH = 14 – 10.56 = 3.44<\/p>\n\n\n\n Next, we use the pOH to calculate the concentration of hydroxide ions (OH\u207b): [OH\u2212]=10\u2212pOH=10\u22123.44=3.60\u00d710\u22124\u2009M[OH\u207b] = 10^{-pOH} = 10^{-3.44} = 3.60 \\times 10^{-4} \\, \\text{M}<\/p>\n\n\n\n Methylamine (CH\u2083NH\u2082) is a weak base and reacts with water to form hydroxide ions and methylammonium ions (CH\u2083NH\u2083\u207a): CH\u2083NH\u2082+H\u2082O\u21ccCH\u2083NH\u2083++OH\u2212\\text{CH\u2083NH\u2082} + \\text{H\u2082O} \\rightleftharpoons \\text{CH\u2083NH\u2083}\u207a + \\text{OH}\u207b<\/p>\n\n\n\n The base dissociation constant (K\u2093) for methylamine is: Kb=[CH3NH3+][OH\u2212][CH3NH2]K_b = \\frac{[CH\u2083NH\u2083\u207a][OH\u207b]}{[CH\u2083NH\u2082]}<\/p>\n\n\n\n From the information, we know that the concentration of OH\u207b is 3.60\u00d710\u22124\u2009M3.60 \\times 10^{-4} \\, \\text{M}. This corresponds to the amount of CH\u2083NH\u2083\u207a produced at equilibrium, and since methylamine reacts in a 1:1 ratio with OH\u207b, the concentration of CH\u2083NH\u2082 at equilibrium is the same: [CH3NH2]=3.60\u00d710\u22124\u2009M[CH\u2083NH\u2082] = 3.60 \\times 10^{-4} \\, \\text{M}<\/p>\n\n\n\n To find the mass of methylamine, we use the formula: mass=molarity\u00d7molar mass\u00d7volume\\text{mass} = \\text{molarity} \\times \\text{molar mass} \\times \\text{volume}<\/p>\n\n\n\n The molar mass of CH\u2083NH\u2082 is: Molar mass of CH\u2083NH\u2082=12.01\u2009(C)+3\u00d71.008\u2009(H)+14.01\u2009(N)=31.06\u2009g\/mol\\text{Molar mass of CH\u2083NH\u2082} = 12.01 \\, (\\text{C}) + 3 \\times 1.008 \\, (\\text{H}) + 14.01 \\, (\\text{N}) = 31.06 \\, \\text{g\/mol}<\/p>\n\n\n\n Now, calculating the mass in 100.0 mL (0.100 L) of solution: mass=(3.60\u00d710\u22124\u2009mol\/L)\u00d7(31.06\u2009g\/mol)\u00d7(0.100\u2009L)=1.12\u00d710\u22123\u2009g\\text{mass} = (3.60 \\times 10^{-4} \\, \\text{mol\/L}) \\times (31.06 \\, \\text{g\/mol}) \\times (0.100 \\, \\text{L}) = 1.12 \\times 10^{-3} \\, \\text{g}<\/p>\n\n\n\n Thus, the mass of methylamine in 100.0 mL of the solution is 1.1 mg<\/strong> (rounded to 2 significant digits).<\/p>\n","protected":false},"excerpt":{"rendered":" An aqueous solution of methylamine CH3NH2 has a pH of 10.56 . How many grams of methylamine are there in 100.0mL of the solution? Round your answer to 2 significant digits. The correct answer and explanation is: To find the amount of methylamine (CH\u2083NH\u2082) in the solution, we must first determine the concentration of methylamine […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-46418","post","type-post","status-publish","format-standard","hentry","category-quiz-questions"],"_links":{"self":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/46418","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/comments?post=46418"}],"version-history":[{"count":1,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/46418\/revisions"}],"predecessor-version":[{"id":46423,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/46418\/revisions\/46423"}],"wp:attachment":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/media?parent=46418"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/categories?post=46418"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/tags?post=46418"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Step 1: Determine the pOH and pKb<\/h3>\n\n\n\n
Step 2: Set up the equilibrium expression for methylamine<\/h3>\n\n\n\n
Step 3: Find the concentration of methylamine<\/h3>\n\n\n\n
Step 4: Calculate the mass of methylamine<\/h3>\n\n\n\n