Group IV Cation Analysis جداسازی کاتیون های گروه 4 Valdosta State University Purpose هدف To determine which group IV ions are present in an unknown solution. مقصود ما این است که کاتیون های گروه 4 موجود در یک محلول مجهول را شناسایی کنیم

Valdosta State University Background For this experiment,we need the group IV ions that are: Na +, K +, Ba 2+, Ca 2+, Mg 2+. برای این آزمایش ما به کاتیون های گروه 4 نیاز داریم که عبارت اند از سدیم،پتاسیم،باریم،کلسیم،منیزیم These are ions which are left after groups I – III have precipitated. یون های گروه 4 که در سمت چپ بعد از گروه یک تا 3 هستند رسوب میدهند

Valdosta State University Background – Group IV Separation Scheme نقشه جداسازی کاتیون های گروه 4

Valdosta State University Group IV Unknown Flame Test K + lavender flame Flame Test Na + orange-yellow flame A – Flame test for Na + and K + تست شعله برای شناسایی سدیم و پتاسیم محلولی از نمک های سدیم و پتاسیم نات معلوم در اختیار داریم یک روش برای تععین وجود این یون ها آزمون شعله است

Valdosta State University K HC 2 H 3 O 2, K 2 CrO 4 BaCrO 4 yellow ppt. Ba 2+ 6M HCl Flame Test apple - green BaSO 4 white ppt. 6M H 2 SO 4 B – Test for Ba 2+ The formation of a yellow precipitate on the addition of potassium chromate indicates the presence of the barium ion. با اضافه کردن پتاسیم کرومات رسوب زرد رنگی تشکیل میشود که نشان دهنده وجود یون باریم است. Ba 2+ (aq) + K 2 CrO 4 (aq)  BaCrO 4 (s) + 2K + (aq)

Valdosta State University A flame test (apple green) is used to confirm the presence of the ion. تست شعله که به رنگ سیب سبزرنگ درمی آید برای تائید وجود این یون به کار میرود. Ba 2+ (aq) + H 2 SO 4 (aq)  BaSO 4 (s) + 2H + (aq) تست نهایی برای باریم نوعی رسوب سفید رنگ است که با اضافه کردن محلولی از سولفات به دست می آید

Valdosta State University Ca 2+, Mg 2+ CaC 2 O 4 (NH 4 ) 2 C 2 O 4 Mg 2+ Flame test red-orange 6M HCl C – Test for Ca 2+ The calcium ion is separated from magnesium by precipitating calcium oxalate. Ca 2+ (aq) + (NH 4 ) 2 C 2 O 4 (aq)  CaC 2 O 4 (s) + 2NH 4 + (aq)

Valdosta State University C – Test for Ca 2+ A flame test (red-orange flame) is used to confirm the presence of the calcium ion. Ca 2+, Mg 2+ CaC 2 O 4 (NH 4 ) 2 C 2 O 4 Mg 2+ Flame test red-orange 6M HCl

Valdosta State University C – Test for Mg 2+ The magnesium ion is precipitated as a white solid (ammonium phosphate) in an alkaline solution. Ca 2+, Mg 2+ CaC 2 O 4 K2C2O4K2C2O4 Mg 2+ Flame test red-orange 6M HCl Mg 2+ (aq) + NH 3 (aq) + HPO 4 2- (aq)  MgNH 4 PO 4 (s) MgNH 4 PO 4 – 6H 2 O white ppt. NH 3 (aq) Na 2 HPO 4 (aq)

Procedure – Experiment 12 - For this experiment, work individually.

Procedure – Group IV Separation Scheme Valdosta State University A – Flame test for Na + and K + 1.Heat 2 mL of a Group IV cation known or unknown in an evaporating dish until a moist residue remains. 2.Add 20 drops of 6 M HCl to this moist residue, and again heat in the evaporating dish until a moist residue remains. 3.While the moist residue cools, obtain a piece of Nichrome wire and make a small loop in the end of the wire. 4.Clean the wire by dipping the loop in concentrated (12 M) HCl, and inserting the wire into the hottest part of the flame. 5.Keep the wire in the flame until the wire imparts no color to the flame. Group IV Unknown Flame Test Na + orange-yellow flame Flame Test K + lavender flame

Procedure – Group IV Separation Scheme Valdosta State University A – Flame test for Na + and K + 6.Dip the loop of the wire in the moist residue. 7.Place the loop of the wire in the flame and observe the color of the flame. A brilliant orange-yellow flame that persists is a positive test for sodium ion. 8.Clean the wire (steps 4, 5) 9.Dip the wire into the moist residue, and insert the loop end of the wire into the hottest part of the flame. Observe the flame through a cobalt blue filter. 10.A lavender flame observed through the cobalt blue filter confirms potassium ion Group IV Unknown Flame Test Na + orange-yellow flame Flame Test K + lavender flame

Procedure – Group IV Separation Scheme Valdosta State University B – Test for Ba 2+ 1.Obtain 2 mL of fresh Group IV cation known (or unknown) solution in a medium test tube and add 2 drops of 2 M NH 4 C 2 H 3 O 2 and 1 drop of 6 M HC 2 H 3 O 2. 2.Add 1 drop of 1 M K 2 CrO 4 to the sample. 3.A yellow precipitate means that barium ion is likely to be present. 4.Centrifuge the solution and decant. 5.Save the decantate for Part C. HC 2 H 3 O 2, K 2 CrO 4 BaCrO 4 yellow ppt. Ba 2+ 6M HCl Flame Test apple - green BaSO 4 white ppt. 6M H 2 SO 4

Procedure – Group IV Separation Scheme Valdosta State University B – Test for Ba 2+ 6.To the precipitate, add 6 M HCl dropwise until the precipitate dissolves, then add 10 more drops. 7.Transfer 5 drops of the solution to an evaporating dish, and heat until a moist residue remains. Perform a flame test on the moist residue. 8.A weak, apple-green flame is also an indication that barium ion is present. 9.To the remainder of the solution, add 10 drops 6 M H 2 SO A white precipitate also indicates barium ion. HC 2 H 3 O 2, K 2 CrO 4 BaCrO 4 yellow ppt. Ba 2+ 6M HCl Flame Test apple - green BaSO 4 white ppt. 6M H 2 SO 4

Procedure – Group IV Separation Scheme Valdosta State University C – Test for Ca 2+ 1.Add 6 M NH 3 to the supernatant from Part B until the solution is basic to litmus. 2.Add 10 drops of saturated (NH 4 ) 2 C 2 O 4 and stir. 3.A white precipitate indicates the presence of calcium ion. 4.If no precipitate appears immediately, warm the solution in a water bath. 5.If a precipitate forms, centrifuge and decant. 6.Save the decantate for Part D. Ca 2+, Mg 2+ CaC 2 O 4 (NH 4 ) 2 C 2 O 4 Mg 2+ Flame test red-orange 6M HCl

Procedure – Group IV Separation Scheme Valdosta State University C – Test for Ca 2+ 7.Add 6 M HCl to the white precipitate until it dissolves, then add 10 more drops. 8.Transfer the solution to an evaporating dish and heat until a moist residue remains. 9.Perform a flame test on the moist residue, 10.A fleeting red-orange flame is an indication that calcium is present. Ca 2+, Mg 2+ CaC 2 O 4 (NH 4 ) 2 C 2 O 4 Mg 2+ Flame test red-orange 6M HCl

Procedure – Group IV Separation Scheme Valdosta State University D – Test for Mg 2+ 1.If the decantate from Part C is not basic, add 6 M NH 3 until the solution is basic to litmus, then add 5 drops more. 2.Add 10 drops 1 M Na 2 HPO 4 and set the solution aside for approximately ten minutes. 3.A white, crystalline precipitate of MgNH 4 PO 4 (looks like snow) confirms the presence of magnesium. Ca 2+, Mg 2+ CaC 2 O 4 (NH 4 ) 2 C 2 O 4 Mg 2+ Flame test red-orange 6M HCl MgNH 4 PO 4 – 6H 2 O white ppt. NH 3 (aq) Na 2 HPO 4 (aq)

Safety Valdosta State University Concentrated HCl causes severe burns to the skin which can take weeks to completely heal and also can cause serious eye damage. This chemical also destroys books and clothing. If you get any on you, wash the affected area(s) with copious quantities of water for ten minutes. Other 6 M acids can cause burns. If you spill some on your skin, wash the affected area with water for five minutes.

Waste Disposal Because the solutions used in this experiment contain ions that can hazardous to the environment and to human health, all solutions and precipitates used in this experiment must be placed in the container marked "Recovered Metals and Metal Ions". Valdosta State University