{"id":2300,"date":"2023-10-02T12:03:52","date_gmt":"2023-10-02T12:03:52","guid":{"rendered":"http:\/\/localhost\/ecole9ja\/?p=2300"},"modified":"2023-10-02T12:15:14","modified_gmt":"2023-10-02T12:15:14","slug":"week-4-and-5-ss1-second-term-chemistry-notes","status":"publish","type":"post","link":"https:\/\/ecolebooks.com\/nigeria\/posts\/week-4-and-5-ss1-second-term-chemistry-notes\/","title":{"rendered":"Week 4 and 5 – SS1 Second Term Chemistry Notes"},"content":{"rendered":"

\u00a0
\n\u00a0
\n\u00a0WEEK 4 & 5
\n<\/strong>STATE,ILLUSTRATION AND VERIFICATION OF CHEMICAL LAWS
\n<\/strong>Law of Conservation of Mass
\n<\/strong>
\n\u00a0In 1774, Joseph Priestley isolated the gas oxygen by heating mercuric oxide. Soon thereafter, Antoine Lavoisier claimed that oxygen is the key substance involved in combustion (burning). He also demonstrated that when combustion is carried out in a closed container, the mass of the final products of combustion exactly equals the mass of the starting reactants. This led to the statement of the Law of Conservation of Mass:
\nLaw of Conservation of Mass
\n<\/strong>Mass is neither created nor destroyed in chemical reactions.<\/p>\n

\u00a0In an experiment, 63.5g of copper combines with 16g of oxygen to give 79.5g of cupric oxide (a black oxide of copper). This is in agreement with the law of conservation of mass.<\/p>\n

\u00a0Science today knows that matter can be converted into energy (and vice-versa). Hence, during all chemical and physical changes, the total mass+energy before the change is equal to the total mass+energy after the change. Still, as there is no detectable change in mass in an ordinary chemical reaction, the law of conservation of mass is still valid.<\/p>\n

\u00a0Silicon dioxide, made up of elements silicon and oxygen, contains 46.7% by mass of silicon. With what mass of oxygen will 10g of silicon combine?
\n100g of silicon dioxide contains : 46.7g of silicon,
\n or : (100 \u2013 46.7) i.e. 53.3g of oxygen.<\/p>\n

\u00a0\u2234 10g of silicon will contain 10100\u2009\u00d7\u200953.3=5.33g of oxygen.
\nLaw of Definite Proportions \/ Constant Composition
\n<\/strong>
\n\u00a0In the years following Lavoisier, the French chemist Joseph Proust formulated a second fundamental law of chemical science \u2013 the Law of Definite Proportions.<\/p>\n

\t\t\tLaw of Definite Proportions (Law of Constant Composition)
\n<\/strong>In a given compound, the constituent elements are always combined in the same proportions by mass, regardless of the origin or mode of preparation of the compound.<\/p>\n

\u00a0What this law means is that when elements react chemically, they combine in specific proportions, not in random proportions.<\/p>\n

\u00a0A sample of pure water, whatever the source, always contains 88.9% by mass of oxygen and 11.1% by mass of hydrogen.<\/p>\n

\u00a0The compound cupric oxide may be prepared by any one of the following methods \u2013
\n\u2022 Heating copper in oxygen.
\n\u2022 Dissolving copper in nitric acid and igniting the cupric nitrate formed.
\n\u2022 Dissolving copper in nitric acid, precipitating cupric hydroxide, and strongly heating the cupric hydroxide.
\n\u2013 and in each case, the ratio copper:oxygen by mass is always constant.<\/p>\n

\u00a02.16g of mercuric oxide gave on decomposition 0.16g of oxygen. In another experiment 16g of mercury was obtained by the decomposition of 17.28g of mercuric oxide. Show that these data conform to the law of definite proportions.<\/p>\n

\u00a0Experiment 1:<\/p>\n

\u00a0Mass of mercuric oxide = 2.16g
\nMass of oxygen evolved from it = 0.16g
\n\u2234 Mass of silicon in the compound = 2.16 – 0.16 = 2.00
\n\u2234 silicon:oxygen ratio = 2.000.16 = 12.5 : 1<\/p>\n

\u00a0Experiment 2:
\nMass of mercuric oxide = 17.28g
\nMass of silicon in it = 16.00g \u2234 Mass of oxygen in the compound = 17.28 – 16.00 = 1.28g
\n\u2234 silicon:oxygen ratio = 16.001.28 = 12.5 : 1
\nIn both cases, the silicon to oxygen ratio is the same, thus conforming to the law of definite proportions.<\/p>\n

\u00a0QUESTIONS
\n<\/strong> (a) Two different sample, 1 and 2 of Zinc oxide were obtained from different sources. When heated in a stream of hydrogen they wre reduced to yield the results below.<\/p>\n

\u00a0<\/p>\n

\n\n\n\n\n\n
Zinc Oxide<\/td>\nMass of Oxide<\/td>\nMass of Zinc left<\/td>\n<\/tr>\n
Sample 1<\/td>\n20.0g<\/td>\n16.22g<\/td>\n<\/tr>\n
Sample 2<\/td>\n26.4g<\/td>\n21.7g<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Show that the result above explains the law of constant composition.<\/p>\n

\u00a0(b) If 12.0g of carbon is heated in air, the mass of the product obtained could either be 44.0g or 28.0g depending on the amount of oxygen present. What law does this information support?<\/p>\n

\u00a0
\n\u00a0\u00a0\u00a0\u00a0
\n\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"

\u00a0 \u00a0 \u00a0WEEK 4 & 5 STATE,ILLUSTRATION AND VERIFICATION OF CHEMICAL LAWS Law of Conservation…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1,196],"tags":[],"class_list":["post-2300","post","type-post","status-publish","format-standard","hentry","category-posts","category-second-term-ss1-chemistry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/posts\/2300","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/comments?post=2300"}],"version-history":[{"count":1,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/posts\/2300\/revisions"}],"predecessor-version":[{"id":2301,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/posts\/2300\/revisions\/2301"}],"wp:attachment":[{"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/media?parent=2300"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/categories?post=2300"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/tags?post=2300"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}