umroh februari,

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


Late in April, after Native American actors walked off in disgust from the set of Adam Sandler’s latest film, a western sendup that its distributor, Netflix, has defended as being equally offensive to all, a glow of pride spread through several Native American communities.

Tantoo Cardinal, a Canadian indigenous actress who played Black Shawl in “Dances With Wolves,” recalled thinking to herself, “It’s come.” Larry Sellers, who starred as Cloud Dancing in the 1990s television show “Dr. Quinn, Medicine Woman,” thought, “It’s about time.” Jesse Wente, who is Ojibwe and directs film programming at the TIFF Bell Lightbox in Toronto, found himself encouraged and surprised. There are so few film roles for indigenous actors, he said, that walking off the set of a major production showed real mettle.

But what didn’t surprise Mr. Wente was the content of the script. According to the actors who walked off the set, the film, titled “The Ridiculous Six,” included a Native American woman who passes out and is revived after white men douse her with alcohol, and another woman squatting to urinate while lighting a peace pipe. “There’s enough history at this point to have set some expectations around these sort of Hollywood depictions,” Mr. Wente said.

The walkout prompted a rhetorical “What do you expect from an Adam Sandler film?,” and a Netflix spokesman said that in the movie, blacks, Mexicans and whites were lampooned as well. But Native American actors and critics said a broader issue was at stake. While mainstream portrayals of native peoples have, Mr. Wente said, become “incrementally better” over the decades, he and others say, they remain far from accurate and reflect a lack of opportunities for Native American performers. What’s more, as Native Americans hunger for representation on screen, critics say the absence of three-dimensional portrayals has very real off-screen consequences.

“Our people are still healing from historical trauma,” said Loren Anthony, one of the actors who walked out. “Our youth are still trying to figure out who they are, where they fit in this society. Kids are killing themselves. They’re not proud of who they are.” They also don’t, he added, see themselves on prime time television or the big screen. Netflix noted while about five people walked off the “The Ridiculous Six” set, 100 or so Native American actors and extras stayed.


But in interviews, nearly a dozen Native American actors and film industry experts said that Mr. Sandler’s humor perpetuated decades-old negative stereotypes. Mr. Anthony said such depictions helped feed the despondency many Native Americans feel, with deadly results: Native Americans have the highest suicide rate out of all the country’s ethnicities.

The on-screen problem is twofold, Mr. Anthony and others said: There’s a paucity of roles for Native Americans — according to the Screen Actors Guild in 2008 they accounted for 0.3 percent of all on-screen parts (those figures have yet to be updated), compared to about 2 percent of the general population — and Native American actors are often perceived in a narrow way.

In his Peabody Award-winning documentary “Reel Injun,” the Cree filmmaker Neil Diamond explored Hollywood depictions of Native Americans over the years, and found they fell into a few stereotypical categories: the Noble Savage, the Drunk Indian, the Mystic, the Indian Princess, the backward tribal people futilely fighting John Wayne and manifest destiny. While the 1990 film “Dances With Wolves” won praise for depicting Native Americans as fully fleshed out human beings, not all indigenous people embraced it. It was still told, critics said, from the colonialists’ point of view. In an interview, John Trudell, a Santee Sioux writer, actor (“Thunderheart”) and the former chairman of the American Indian Movement, described the film as “a story of two white people.”

“God bless ‘Dances with Wolves,’ ” Michael Horse, who played Deputy Hawk in “Twin Peaks,” said sarcastically. “Even ‘Avatar.’ Someone’s got to come save the tribal people.”

Dan Spilo, a partner at Industry Entertainment who represents Adam Beach, one of today’s most prominent Native American actors, said while typecasting dogs many minorities, it is especially intractable when it comes to Native Americans. Casting directors, he said, rarely cast them as police officers, doctors or lawyers. “There’s the belief that the Native American character should be on reservations or riding a horse,” he said.

“We don’t see ourselves,” Mr. Horse said. “We’re still an antiquated culture to them, and to the rest of the world.”

Ms. Cardinal said she was once turned down for the role of the wife of a child-abusing cop because the filmmakers felt that casting her would somehow be “too political.”

Another sore point is the long run of white actors playing American Indians, among them Burt Lancaster, Rock Hudson, Audrey Hepburn and, more recently, Johnny Depp, whose depiction of Tonto in the 2013 film “Lone Ranger,” was viewed as racist by detractors. There are, of course, exceptions. The former A&E series “Longmire,” which, as it happens, will now be on Netflix, was roundly praised for its depiction of life on a Northern Cheyenne reservation, with Lou Diamond Phillips, who is of Cherokee descent, playing a Northern Cheyenne man.

Others also point to the success of Mr. Beach, who played a Mohawk detective in “Law & Order: Special Victims Unit” and landed a starring role in the forthcoming D C Comics picture “Suicide Squad.” Mr. Beach said he had come across insulting scripts backed by people who don’t see anything wrong with them.

“I’d rather starve than do something that is offensive to my ancestral roots,” Mr. Beach said. “But I think there will always be attempts to drawn on the weakness of native people’s struggles. The savage Indian will always be the savage Indian. The white man will always be smarter and more cunning. The cavalry will always win.”

The solution, Mr. Wente, Mr. Trudell and others said, lies in getting more stories written by and starring Native Americans. But Mr. Wente noted that while independent indigenous film has blossomed in the last two decades, mainstream depictions have yet to catch up. “You have to stop expecting for Hollywood to correct it, because there seems to be no ability or desire to correct it,” Mr. Wente said.

There have been calls to boycott Netflix but, writing for Indian Country Today Media Network, which first broke news of the walk off, the filmmaker Brian Young noted that the distributor also offered a number of films by or about Native Americans.

The furor around “The Ridiculous Six” may drive more people to see it. Then one of the questions that Mr. Trudell, echoing others, had about the film will be answered: “Who the hell laughs at this stuff?”

Native American Actors Work to Overcome a Long-Documented Bias

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