TEORI ASAM BASA KIMIA DASAR 2012 Apa yang terpikir ketika anda mendengar kata “asam” atau “basa” KIMIA DASAR 2012
ASAM BASA Apa yang terpikir ketika anda mendengar kata “asam” atau “basa”
ASAM BASA Menurut anda apakah zat dalam slide berikut ini tergolong asam?
ASAM BASA Bagaimana dengan senyawa berikut?
ASAM BASA
ASAM BASA
ASAM BASA
ASAM BASA
KEKUATAN ASAM BASA
REACTION OF ZINK WITH STRONG VS WEAK ACID ASAM KUAT REACTION OF ZINK WITH STRONG VS WEAK ACID ASAM LEMAH
Sifat umum ACIDS Berasa asam Merubah lakmus React with active metals – Fe, Zn React with bases BASES Berasa pahit Merubah lakmus Feel soapy or slippery (react with fats to make soap) React with acids blue to red red to blue
Teori ASAM BASA Svante August ARRHENIUS (Swedish) 1859 - 1927 Johannes Nicolaus BRØNSTED (Danish) 1879 - 1947 Thomas Martin LOWRY (English) 1874 - 1936 Gilbert Newton LEWIS (American) 1875 - 1946
DEFINISI 1. TEORI ARRHENIUS : “ ASAM MERUPAKAN SENYAWA YANG DAPAT MENGHASILKAN ION HIDROGEN H+ BILA DILARUTKAN KEDALAM AIR”. Ion hidrogen (proton) dalam molekul air tidak dapat berdiri sendiri dan bergabung dengan cara mengganti sepasang elektron sunyi oksigen dari mol ekul air dan disebut ion HIDRONIUM Setiap molekul HCl hanya dapat menghasilkan 1 ion H+ disebut valensi asam. Asam semacam ini disebut juga asam monoprotik. Kalau menghasilkan 2 ion H+ disebut asam diprotik DAN lebih dari 2 disebut poliprotik
DEFINISI 1. Arrhenius
DEFINISI 1. Arrhenius “BASA MERUPAKAN SENYAWA YANG DAPAT MEMBERIKAN ION HIDROKSIDA (OH-) BILA DILARUTKAN DALAM AIR” Untuk menunjukkan sifat basanya larutan NH3 sering ditulis NH4OH
DEFINISI 1. Arrhenius
2. TEORI BRØNSTED-LOWRY An acid is a proton donor, any species that donates an H+ ion. An acid must contain H in its formula; HNO3 and H2PO4- are two examples, all Arrhenius acids are Brønsted-Lowry acids. A base is a proton acceptor, any species that accepts an H+ ion. A base must contain a lone pair of electrons to bind the H+ ion; a few examples are NH3, CO32-, F -, as well as OH -. Brønsted-Lowry bases are not Arrhenius bases, but all Arrhenius bases contain the Brønsted-Lowry base OH-. Therefore in the Brønsted-Lowry perspective, one species donates a proton and another species accepts it: an acid-base reaction is a proton transfer process. Acids donate a proton to water Bases accept a proton from water
Molecular model: Two water (h2o) molecules react to form H3O+ and OH- Molecular model: The reaction of an acid HA with water to form H3O+ and a conjugate base. Acid (HA) Base (H2O) Conjugate Conjugate acid (H3O+) base (A-)
2. TEORI BRØNSTED-LOWRY
2. TEORI BRØNSTED-LOWRY
2. TEORI BRØNSTED-LOWRY
The Conjugate Pairs in Some Acid-Base Reactions Acid + Base Base + Acid Conjugate Pair Reaction 1 HF + H2O F– + H3O+ Reaction 2 HCOOH + CN– HCOO– + HCN Reaction 3 NH4+ + CO32– NH3 + HCO3– Reaction 4 H2PO4– + OH– HPO42– + H2O Reaction 5 H2SO4 + N2H5+ HSO4– + N2H62+ Reaction 6 HPO42– + SO32– PO43– + HSO3–
Conjugate pairs HCl Cl- CH3COOH CH3COO- NH4+ NH3 HNO3 NO3- H+ transfer 2. TEORI BRØNSTED-LOWRY Conjugate pairs HCl Cl- CH3COOH CH3COO- NH4+ NH3 HNO3 NO3- How does a conjugate pair differ? H+ transfer
2. TEORI BRØNSTED-LOWRY SENYAWA AMFOTER
3. TEORI LEWIS Lewis acid - a substance that accepts an electron pair Lewis base - a substance that donates an electron pair
Formation of hydronium ion is also an excellent example. 3. TEORI LEWIS Formation of hydronium ion is also an excellent example. Electron pair of the new O-H bond originates on the Lewis base.
3. TEORI LEWIS
3. TEORI LEWIS
3. TEORI LEWIS
RANGKUMAN Arrehenius Brønsted-Lowry Lewis ASAM – produce H+ BASA - produce OH- ASAM – donate H+ BASA – accept H+ ASAM – accept e- pair BASA – donate e- pair Arrehenius Unt. senyawa yg hanya larut dalam air Brønsted-Lowry Mencakup senyawa yg tak larut dalam air Lewis Digunakan dalam kimia organik, wider range of substances
CONTOH
KEKUATAN ASAM BASA
KEKUATAN ASAM BASA
ASAM DAN REAKSI IONISASINYA
BASA DAN REAKSI IONISASINYA
CONTOH SENYAWA AMFOTER
ASAM DAN REAKSI IONISASINYA
ASAM DAN REAKSI IONISASINYA
TETAPAN KESETIMBANGAN
TETAPAN KESETIMBANGAN
TETAPAN KESETIMBANGAN
TETAPAN KESETIMBANGAN
TETAPAN KESETIMBANGAN
TETAPAN KESETIMBANGAN Ka HCN = 17 x 10-10, Ka HOCl = 3 x 10-8, Ka CH3COOH = 76 x 10-5
TETAPAN KESETIMBANGAN
DERAJAT IONISASI
DERAJAT IONISASI
DERAJAT IONISASI
DERAJAT IONISASI
DERAJAT IONISASI Jika diketahui Ka asam asetat adalah 1,76 x 10-5: Berapakah derajat ionisasi ( ) asam asetat pada konsentrasi 0,1 M dan 0,01 M Berapakah konsentrasi ion H+ pada kedua konsentrasi tersebut dengan memperhatikan derajat ionisasinya ( )?
DERAJAT IONISASI
DERAJAT IONISASI
DISOSIASI ASAM POLIVALEN
APA YANG DIMAKSUD DG pH Skala untuk mengukur konsentrasi ion hidronium [H+] dalam suatu larutan, dinyatakan dalam skala Logaritma mencakup faktor 10. Larutan dengan pH 1 adalah 10 kali lebih kuat daripada larutan dengan pH 2 Larutan dgn pH 1 mempunyai [H+] 0.1 mol/L atau 10-1 Larutan dgn pH 3 mempunyai [H+] 0.001 mol/L atau 10-3 Larutan dgn pH 7 mempunyai [H+] 0.0000001 mol/L atau 10-7
APA YANG DIMAKSUD DG pH pH = −log[H3O+ ] [H3O+] and pH Ion hidronium biasanya diekspresikan sebagai pH pH is defined as the negative base-10 logarithm of the hydronium ion concentration. The p stands for potential, or power. The H stands for the chemical symbol for hydrogen. pH = −log[H3O+ ] Nilai pH rendah maka konsentrasi ion hidronium tinggi.
ALAT PENGUKUR pH
ALAT PENGUKUR pH ASAM ASETAT AMONIAK
ALAT PENGUKUR pH (a) pH paper (b) Electrodes of a pH meter
10-pH = [H3O+] L A T I H A N [H3O+] = 10-3.12 = 7.6 x 10-4 M Jika pH Coke 3.12, [H3O+] = ??? Karena pH = - log [H3O+] lalu - pH = log [H3O+] Antilog (10x) kedua sisi Akan didapatkan 10-pH = [H3O+] [H3O+] = 10-3.12 = 7.6 x 10-4 M
L A T I H A N Q1: Calculate the pH of a solution if [H3O+] = 2.7 x 10-4 M pH = -log[H3O+] pH = -log(2.7 x 10-4) = 3.57 Q2: Find the hydrogen ion concentration of a solution if its pH is 11.62. [H3O+] = 10-pH [H3O+] = 10-11.62 = 2.4 x 10-12M Q3: Find the pOH and the pH of a solution if its hydroxide ion concentration is 7.9 x 10-5M pOH = -log[OH-] pOH = -log(7.9 x 10-5) = 4.10 pH + pOH = 14 pH = 14 - 4.10 pH = 9.9
L A T I H A N Suatu larutan mempunyai pH 8.5. Berapa konsentrasi ion hidrogen dalam larutan? pH = - log [H+] 8.5 = - log [H+] -8.5 = log [H+] Antilog -8.5 = antilog (log [H+]) 10-8.5 = [H+] 3.16 X 10-9 = [H+]
(Remember that the [ ] mean Molarity) pH = - log [H+] (Remember that the [ ] mean Molarity) Example: If [H+] = 1 X 10-10 pH = - log 1 X 10-10 pH = - (- 10) pH = 10 Example: If [H+] = 1.8 X 10-5 pH = - log 1.8 X 10-5 pH = - (- 4.74) pH = 4.74
[H3O+], [OH-] and pH What is the pH of the 0.0010 M NaOH solution? [OH-] = 0.0010 (or 1.0 X 10-3 M) pOH = - log 0.0010 pOH = 3 pH = 14 – 3 = 11
LATIHAN
pH LARUTAN GARAM Garam yang terbentuk dari reaksi ASAM kuat dan BASA kuat Garam yang terbentuk dari reaksi ASAM lemah dan BASA kuat
Garam yang terbentuk dari reaksi BASA lemah dan ASAM kuat Garam yang terbentuk dari reaksi BASA lemah dan ASAM lemah
KCl berasal dari asam dan basa kuat maka bersifat netral karena tidak terhidrolisis B. KCN berasal dari basa kuat dan asam lemah, CN- terhidrolisis menghasilkan OH- sehingga larutan garam bersifat basa C. NH4I berasal dari basa lemah dan asam kuat, NH4+ terhidrolisis menghasilkan H+ sehingga larutan garam bersifat asam
(Kw = 10-14)
Menghitung Ka dari pH Larutan asam formiat 0.10 M, HCOOH, pada 25°C pH nya 2.38. Hitung Ka asam formiat pada temperatur tersebut. Telah diketahui bahwa
Menghitung Ka dari pH Untuk menghitung Ka, dibutuhkan semua konsentrasi kesetimbangan . Dari pH, [H3O+] dapat ditentukan, yang sama juga pada [HCOO−],.
Menghitung Ka dari pH pH = –log [H3O+] – 2.38 = log [H3O+] 10-2.38 = 10log [H3O+] = [H3O+] 4.2 10-3 = [H3O+] = [HCOO–]
Menghitung Ka dari pH Dalam bentuk tabel : [HCOOH], M [H3O+], M [HCOO−], M Awal 0.10 Pengionan –4.2 10-3 +4.2 10-3 Setimbang 0.10 – 4.2 10-3 = 0.0958 ~ 0.10 4.2 10-3 4.2 10 - 3 [4.2 10-3] [4.2 10-3] [0.10] Ka = = 1.8 10-4
TIRASI ASAM BASA Acid-base titration is a process for calculating the concentration of a known volume of acid or base.
Sample Problem In this sample titration, we are trying to determine the concentration of 20.00 mL of HCl. In the titration we will be neutralizing the HCl with 0.150 M NaOH.
Setup for titrating an acid with a base
The equivalence point of the titration is reached when equal numbers of moles of hydronium and hydroxide ions have been reacted. When this happens in this titration, the pH of the solution in the flask is 7.0 and the phenolphthalein indicator is colourless. The permanent colour change in the indicator is known as the endpoint of the titration and the titration is over.
Titration Curve
Solve the problem 1st write the equation for the reaction: HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) 2nd solve for the amount of moles of the titrant used. NaOH mol = 0.150 mol/L x 0.02567 L= 3.85 x 10-3 mol NaOH Found in titration experiment 3rd using stoichiometry, solve for the concentration of HCl , knowing it is a 1:1 mole ratio 3.85 x 10-3 mol= 0.192 M 0.02000 L
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