This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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You're on a roll — here are the answers to your questions: 3) Certain basic radicals produce two different types of colored beads with borax due to the formation of different metal metaborates, which can have varying colors depending on the oxidation state of the metal ion and the flame conditions (oxidizing or reducing). The color can also differ when the bead is hot versus cold. First, borax (Na_2B_4O_7 · 10H_2O) loses water and decomposes upon heating to form sodium metaborate and boric anhydride: Na_2B_4O_7 · 10H_2O Na_2B_4O_7 + 10H_2O Na_2B_4O_7 2NaBO_2 + B_2O_3 When a metal salt is introduced, the metal oxide reacts with boric anhydride to form a colored metal metaborate. For example, copper: In an oxidizing flame, copper(II) oxide forms copper(II) metaborate, which is blue when cold: CuO + B_2O_3 oxidizing flame Cu(BO_2)_2 In a reducing flame, copper(II) metaborate is reduced to copper(I) metaborate, which is opaque reddish-brown when cold: 2Cu(BO_2)_2 + C reducing flame 2CuBO_2 + B_2O_3 + CO The different oxidation states (Cu^2+ vs. Cu^+) result in distinct colors. 4) a) Sodium pyroborate: Na_2B_4O_7 (often hydrated as Na_2B_4O_7 · 10H_2O or Na_2B_4O_7 · H_2O) b) Fusion mixture: Na_2CO_3 + K_2CO_3 (a mixture of sodium carbonate and potassium carbonate) 5) Sodium pyroborate (Na_2B_4O_7 · H_2O) is used in the borax bead test to analyze CuSO_4 by forming characteristic colored beads. Step 1: Borax loses water and decomposes upon heating to form sodium metaborate and boric anhydride. Na_2B_4O_7 · H_2O Na_2B_4O_7 + H_2O Na_2B_4O_7 2NaBO_2 + B_2O_3 Step 2: When CuSO_4 is heated, it decomposes to form copper(II) oxide. CuSO_4 CuO + SO_3 Step 3: The copper(II) oxide then reacts with the boric anhydride (B_2O_3) to form copper(II) metaborate. In an oxidizing flame, the bead is blue when cold: CuO + B_2O_3 oxidizing flame Cu(BO_2)_2 (blue when cold) In a reducing flame, the copper(II) metaborate is reduced to copper(I) metaborate, which is opaque reddish-brown when cold: 2Cu(BO_2)_2 + C reducing flame 2CuBO_2 + B_2O_3 + CO (opaque reddish-brown when cold) The distinct colors confirm the presence of copper. 6) To test for the presence of CO_2(g) in a mixture containing carbonates and sulfides salts reacting with dilute H_2SO_4: Step 1: The mixture of salts reacts with dilute H_2SO_4 to produce both CO_2 and H_2S gases. CO_3^2- (aq) + 2H^+ (aq) H_2O (l) + CO_2 (g) S^2- (aq) + 2H^+ (aq) H_2S (g) Step 2: Pass the evolved gas mixture through an acidified solution of potassium dichromate (K_2Cr_2O_7) or lead acetate solution. The H_2S gas will react and be removed, while CO_2 will pass through. Cr_2O_7^2- (aq) + 3H_2S (g) + 8H^+ (aq) 2Cr^3+ (aq) + 3S (s) + 7H_2O (l) (Orange dichromate turns green due to Cr^3+ formation) Alternatively: Pb(CH_3COO)_2 (aq) + H_2S (g) PbS (s) + 2CH_3COOH (aq) (Lead acetate paper turns black due to PbS formation) Step 3: Pass the remaining gas through limewater (Ca(OH)_2 solution). If CO_2 is present, the limewater will turn milky. Ca(OH)_2 (aq) + CO_2 (g) CaCO_3 (s) + H_2O (l) 7) Chemical tests to identify the following gases: Carbon dioxide (CO_2): Pass the gas through limewater (calcium hydroxide solution). It turns milky due to the formation of insoluble calcium carbonate. Ca(OH)_2 (aq) + CO_2 (g) CaCO_3 (s) + H_2O (l) Ammonia (NH_3): Bring a glass rod dipped in concentrated hydrochloric acid near the gas. Dense white fumes of ammonium chloride will be formed. NH_3 (g) + HCl (g) NH_4Cl (s) Alternatively, expose red litmus paper to the gas. It will turn blue as ammonia is alkaline. Hydrogen sulfide (H_2S): Pass the gas through lead acetate solution or hold a piece of filter paper moistened with lead acetate solution in the gas. The paper will turn black due to the formation of lead(II) sulfide. Pb(CH_3COO)_2 (aq) + H_2S (g) PbS (s) + 2CH_3COOH (aq) 8) The caustic soda test involves adding sodium hydroxide (NaOH, commonly known as caustic soda) solution to a solution of a metal salt to identify the metal cation. It relies on the formation of characteristic precipitates and their solubility in excess NaOH. For example, most transition metal ions form colored hydroxide precipitates that are insoluble in excess NaOH (e.g., Fe^2+ gives a dirty green precipitate of Fe(OH)_2, Cu^2+ gives a blue precipitate of Cu(OH)_2). However, amphoteric metal hydroxides like aluminum, zinc, and lead hydroxides initially form precipitates that then redissolve in excess NaOH to form soluble complex ions. Al^3+ (aq) + 3NaOH (aq) Al(OH)_3 (s) + 3Na^+ (aq) Al(OH)_3 (s) + NaOH (aq) Na[Al(OH)_4] (aq) 9) Preliminary tests, even those based solely on physical appearance, are crucial in qualitative analysis because they provide initial, non-conclusive but highly informative clues about the possible presence of certain acid and basic radicals. For instance, the color of a salt can immediately suggest the presence of specific metal ions: a blue salt often indicates Cu^2+ ions, a pale green salt might suggest Fe^2+ or Ni^2+, and a yellow or brown salt could indicate Fe^3+ ions. Similarly, a distinct smell, like the vinegar-like odor of acetates when heated with acid, or the rotten-egg smell of sulfides upon acidification, provides strong indications. While these observations are not definitive proof, they significantly narrow down the possibilities, guiding subsequent, more specific chemical tests and making the overall analysis more efficient. 10) To identify the acid radicals (CO_3^2- and SO_3^2-) in a salt mixture containing Na_2CO_3 and Na_2SO_3 when treated with dilute H_2SO_4: Step 1: Add dilute H_2SO_4 to the salt mixture. Both carbonates and sulfites will react to produce gases. Na_2CO_3 (s) + H_2SO_4 (aq) Na_2SO_4 (aq) + H_2O (l) + CO_2 (g) Na