Suatu larutan HNO2 0,15 M (Ka = 10^-5) dicampurkan dengan larutan KOH 0,1 M. Tentukan berapa pH campuran larutan tersebut jika volume larutan yang direaksikan 200 mL HNO2 dan 150 mL KOH !

<p>Jawab : pH campuran 5</p><p>&nbsp;</p><p>Pembahasan :&nbsp;</p><p>Pada soal diatas menggunakan rumus larutan penyangga atau buffer. Larutan penyangga (dapar) adalah larutan yang mampu mempertahankan derajat keasaman (pH) pada saat asam atau basa dimasukkan dalam suatu larutan. Larutan penyangga disebut juga “<i>buffer”&nbsp;</i>atau “penahan”.</p><p>Pada soal tersebut diatas maka akan terbentuk larutan penyangga asam (HNO2-KNO2)</p><p>Rumus yang digunakan :</p><p>H⁺ = Ka x (n asam lemah/n garam)</p><p>Keterangan :</p><p>H⁺ &nbsp;= konsentrasi asam (M)</p><p>Ka = tetapan ionisasi asam</p><p>n asam lemah = mol asam lemah</p><p>n garam = mol garam</p><p>&nbsp;</p><p>Penghitungan :&nbsp;</p><p>Diketahui :</p><p>V HNO2 = &nbsp;200 ml</p><p>MHNO2 = 0,15 M</p><p>Ka = 10^-5</p><p>MKOH = 0,1 M</p><p>VKOH = 150 ml</p><p>Ditanya : pH campuran</p><p>Jawab :&nbsp;</p><p>&nbsp;Persamaan Reaksi :</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;KOH &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;+ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;HNO2 - &nbsp; &nbsp; ---&gt; KNO2 &nbsp; &nbsp; &nbsp;+ &nbsp; &nbsp;H2O</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 0,1 M. 150 ml &nbsp; &nbsp; 0,15M. 200 ml &nbsp; &nbsp; &nbsp;</p><p>Mula-mula &nbsp; &nbsp;15 mmol &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 30 mmol &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; - &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;-</p><p>Reaksi &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 15 mmol &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 15 mmol &nbsp; &nbsp; &nbsp;15 mmol &nbsp; &nbsp; &nbsp;15 mmol</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; -------------------------------------------------------------------</p><p>Sisa &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; - &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 15 mmol &nbsp; &nbsp; &nbsp;15 mmol &nbsp; &nbsp;15 mmol</p><p>mol asam HNO2 = 15 mmol</p><p>mol garam KNO2 = 15 mol</p><p>H^+&nbsp; = Ka x (n asam lemah/n garam)</p><p>H⁺ = 10^-5. (15 mmol/15 mmol)</p><p>H⁺ = 10^-5</p><p>pH = -log H⁺ = - log 10^-5</p><p>pH = 5</p><p>&nbsp;</p><p>Jadi kesimpulannya pH campuran tersebut adalah &nbsp;5</p><p>&nbsp;</p>