indikator Asam Basa

Telah disebutkan bahwa asam telah mempunyai rasa asam, sedangkan basa telah mempunyai rasa pahit. Namun begitu, tidak dianjurkan untuk dapat mengenali asam dan basa dengan, cara mencicipinya, sebab banyak diantaranya yang dapat merusak kulit (korosif) atau bahkan bersifat racun. Asam dan basa juga dapat dikenali dengan menggunakan zat indikator, yaitu zat yang telah meniberi warna berbeda dahlia) lingkungan asam dan lingkungan basa (zat yang warnanya dapat berubah saat berinteraksi atau bereaksi dengan senyawa asam maupun senyawa basa).

Dalam laboratorium kimia, indikator asam-basa yang biasa di gunakan adalah indikator buatan dan indikator alami, Berikut ini penjelasan tentang indikator asam-basa buatan dan indikator asam-basa alami.
Derajat keasaman (pH)

Indikator Tingkat Keasaman Suatu zat asam yang di masukkan ke dalam air akan dapat mengakibatkan bertambahnya ion hidrogen (H+) dalam air dan berkurangnya ion hidroksida (OH- ). Sedangkan pada basa, akan dapat terjadi sebaliknya. Zat basa yang dimasukkan ke dalam air akan dapat mengakibatkan bertambahnya ion hidroksida (OH- ) dan berkurangnya ion hidrogen (H+).

Jumlah ion H+ dan OH- di dalam air dapat di gunakan untuk dapat menentukan derajat keasaman atau kebasaan suatu zat. Semakin asam suatu zat, semakin banyak ion H+ dan semakin sedikit jumlah ion OH- di dalam air. Sebaliknya semakin basa suatu zat, semakin sedikit jumlah ion H+ dan semakin banyak ion OH- di dalam air.
Proses netralisasi

Apabila suatu larutan asam dengan larutan basa akan dicampurkan dalam suatu bejana, maka ion H+ (dari asam) akan bereaksi dengan ion OH- (dari 311 basa) membentuk air. Reaksi antara ion H+ dengan OH- tersebut juga dapat di tuliskan sebagai berikut. H+ + OH- air

ini karena selain air, basil reaksi antara asam dan basa adalah suatu zat yang bersifat netral, yaitu zat yang tidak bersifat asam maupun basa. Zat netral yang di maksudkan di sini adalah garam. Mengingat reaksi netralisasi juga dapat menghasilkan garam, maka reaksi ini juga di kenal dengan istilah reaksi penggaraman. Secara sederhana, reaksi netralisasi atau reaksi penggaraman juga dapat di tuliskan sebagai berikut.

Contoh sederhana dari reaksi penggaraman adalah reaksi antara asam klorida (HC1) dengan natrium hidroksida (NaOH), yang akan dapat membentuk natrium klorida NaCl (garam dapur) dan air. Pada dasarnya, reaksi penggaraman (netralisasi) juga sangat berguna bagi kehidupan manusia.

Reaksi netralisasi tidak hanya terbatas pada pembentukkan garam dan air. Dalam kehidupan sehari-hari banyak dijumpai prinsip atau reaksi netralisasi, termasuk dalam bidang kesehatan dan pertanian. Perhatikan contoh berikut ini : gas-gas sisa, baik yang berasal dari kendaraan bermotor atau pabrik, mengandung gas belerang dioksida dan nitrogen oksida.

Gas-gas ini akan dilepas ke udara sehingga menimbulkan polusi. Gas-gas tersebut juga akan larut dalam titik-titik air di awan sehingga membentuk larutan asam sulfat dan asam nitrat. Ketika terjadi hujan, larutan-larutan ini akan bercampur dan turun bersama hujan. Inilah yang dinamakan dengan hujan asam.

Hujan asam sangat merugikan manusia dan lingkungan. Berikut adalah dampak yang ditimbulkan oleh hujan asam:

    Hujan asam dapat menyebabkan matinya tumbuhan dan ikan. Asam yang telah terdapat dalam air hujan juga dapat bereaksi dengan mineral dalam tanah. Tumbuhan akan menjadi kekurangan mineral sehingga mati atau tidak tumbuh dengan baik. Hujan asam juga dapat melarutkan aluminium dari mineral dalam tanah dan bebatuan, kemudian menghanyutkannya ke sungai sehingga dapat meracuni ikan dan mahluk air lainnya.
    Hujan asam yang bereaksi dengan logam juga dapat merusak jembatan, mobil, kapal laut, dan rangka bangunan. Hujan asam juga dapat merusak bangunan (gedung/ rumah) yang terbuat dari batu kapur.

Editor : Dian Sukmawati


BALTIMORE — In the afternoons, the streets of Locust Point are clean and nearly silent. In front of the rowhouses, potted plants rest next to steps of brick or concrete. There is a shopping center nearby with restaurants, and a grocery store filled with fresh foods.

And the National Guard and the police are largely absent. So, too, residents say, are worries about what happened a few miles away on April 27 when, in a space of hours, parts of this city became riot zones.

“They’re not our reality,” Ashley Fowler, 30, said on Monday at the restaurant where she works. “They’re not what we’re living right now. We live in, not to be racist, white America.”

As Baltimore considers its way forward after the violent unrest brought by the death of Freddie Gray, a 25-year-old black man who died of injuries he suffered while in police custody, residents in its predominantly white neighborhoods acknowledge that they are sometimes struggling to understand what beyond Mr. Gray’s death spurred the turmoil here. For many, the poverty and troubled schools of gritty West Baltimore are distant troubles, glimpsed only when they pass through the area on their way somewhere else.

Officers blocked traffic at Pennsylvania and West North Avenues after reports that a gun was discharged in the area. Credit Drew Angerer for The New York Times

And so neighborhoods of Baltimore are facing altogether different reckonings after Mr. Gray’s death. In mostly black communities like Sandtown-Winchester, where some of the most destructive rioting played out last week, residents are hoping businesses will reopen and that the police will change their strategies. But in mostly white areas like Canton and Locust Point, some residents wonder what role, if any, they should play in reimagining stretches of Baltimore where they do not live.

“Most of the people are kind of at a loss as to what they’re supposed to do,” said Dr. Richard Lamb, a dentist who has practiced in the same Locust Point office for nearly 39 years. “I listen to the news reports. I listen to the clergymen. I listen to the facts of the rampant unemployment and the lack of opportunities in the area. Listen, I pay my taxes. Exactly what can I do?”

And in Canton, where the restaurants have clever names like Nacho Mama’s and Holy Crepe Bakery and Café, Sara Bahr said solutions seemed out of reach for a proudly liberal city.

“I can only imagine how frustrated they must be,” said Ms. Bahr, 36, a nurse who was out with her 3-year-old daughter, Sally. “I just wish I knew how to solve poverty. I don’t know what to do to make it better.”

The day of unrest and the overwhelmingly peaceful demonstrations that followed led to hundreds of arrests, often for violations of the curfew imposed on the city for five consecutive nights while National Guard soldiers patrolled the streets. Although there were isolated instances of trouble in Canton, the neighborhood association said on its website, many parts of southeast Baltimore were physically untouched by the tumult.

Tensions in the city bubbled anew on Monday after reports that the police had wounded a black man in Northwest Baltimore. The authorities denied those reports and sent officers to talk with the crowds that gathered while other officers clutching shields blocked traffic at Pennsylvania and West North Avenues.

Lt. Col. Melvin Russell, a community police officer, said officers had stopped a man suspected of carrying a handgun and that “one of those rounds was spent.”

Colonel Russell said officers had not opened fire, “so we couldn’t have shot him.”

Lambi Vasilakopoulos, right, who runs a casual restaurant in Canton, said he was incensed by last week's looting and predicted tensions would worsen. Credit Drew Angerer for The New York Times

The colonel said the man had not been injured but was taken to a hospital as a precaution. Nearby, many people stood in disbelief, despite the efforts by the authorities to quash reports they described as “unfounded.”

Monday’s episode was a brief moment in a larger drama that has yielded anger and confusion. Although many people said they were familiar with accounts of the police harassing or intimidating residents, many in Canton and Locust Point said they had never experienced it themselves. When they watched the unrest, which many protesters said was fueled by feelings that they lived only on Baltimore’s margins, even those like Ms. Bahr who were pained by what they saw said they could scarcely comprehend the emotions associated with it.

But others, like Lambi Vasilakopoulos, who runs a casual restaurant in Canton, said they were incensed by what unfolded last week.

“What happened wasn’t called for. Protests are one thing; looting is another thing,” he said, adding, “We’re very frustrated because we’re the ones who are going to pay for this.”

There were pockets of optimism, though, that Baltimore would enter a period of reconciliation.

“I’m just hoping for peace,” Natalie Boies, 53, said in front of the Locust Point home where she has lived for 50 years. “Learn to love each other; be patient with each other; find justice; and care.”

A skeptical Mr. Vasilakopoulos predicted tensions would worsen.

“It cannot be fixed,” he said. “It’s going to get worse. Why? Because people don’t obey the laws. They don’t want to obey them.”

But there were few fears that the violence that plagued West Baltimore last week would play out on these relaxed streets. The authorities, Ms. Fowler said, would make sure of that.

“They kept us safe here,” she said. “I didn’t feel uncomfortable when I was in my house three blocks away from here. I knew I was going to be O.K. because I knew they weren’t going to let anyone come and loot our properties or our businesses or burn our cars.”

Baltimore Residents Away From Turmoil Consider Their Role

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