Gas HCN (Mr = 27) adalah gas

yang bersifat racun, yang jika terhirup dapat menyebabkan kematian. Konsentrasi

HCN sebesar 300 mg/Kg di udara sudah dapat mematikan dan konsentrasi itu

disebut dosis mematikan/

Dalam suatu laboratorium kecil

dengan ukuran 5 m x 4 m x 3 m terjadi pencemaran gas HCN sehingga menimbulkan

keracunan.Hitunglah jumlah mol HCN paling sedikit yang ada dalam ruangan

laboratorium tersebut yang dapat menyebabkan kematian…

Keracunan merkuri dapat merusak

syaraf karena di dalam tubuh, merkuri membentuk senyawa kompleks kordinasi 1 : 2

dengan gugus liopil, yang berperan penting dalam metabolisme glukosa. Jika

konsentrasi rata-rata gugus liopil dalam cairan tubuh adalah 1,5 x 10

(Ar Hg = 200)

Proses hidrolisis dapat

berlangsung dalam suasana basa. Pada hidrolisis ini asam lemak yang terbentuk

akan bereaksi dengan basanya membentuk garam. Reaksi hidrolisis ini dikenal

sebagai reaksi penyabunan atau saponifikasi. Garam yang terbentuk dikenal sebagai

sabun. Seorang siswa mereaksikan 4,39 Kg minyak kelapa, 

Reaksi: C₅₇H₉₈O₆

+ 3NaOH → 3C

How Heatwaves Become More Dangerous in Cities

A heatwave is a prolonged period of unusually high temperatures that can affect human health,

infrastructure, and natural ecosystems. Although heatwaves can occur in both rural and urban

areas, their effects are often more severe in cities. This happens because several environmental

and human factors interact to increase and retain heat.

One important factor is the concentration of heat-absorbing materials. Urban areas contain large

amounts of concrete, asphalt, and other hard surfaces. During the day, these materials absorb solar

energy and gradually release it after sunset. As a result, buildings, roads, and pavements can remain

warm long after the air temperature begins to decline. This contributes to the urban heat island

effect, in which cities become significantly warmer than surrounding areas.

The lack of vegetation can make the situation worse. Trees and other plants provide shade and

release water vapor through a process called evapotranspiration. This process consumes energy

and helps cool the surrounding environment. When vegetation is replaced by buildings and paved

surfaces, cities lose an important natural cooling mechanism.

Human activities can add even more heat. Vehicles, industrials equipment, and air-conditioning

systems release waste heat into the environment. During an extreme heat event, the increased use

of air conditioners may provide indoor relief but

Urban design can also influence how effectively heat escapes. Closely spaces buildings may

restrict air movement, allowing warm air to remain trapped between structures. Consequently,

some densely developed neighborhoods may experience higher temperatures than areas with more

open spaces and vegetation.

For these reasons, the severity of an urban heatwave is not determined by temperature alone.

Building materials, vegetation, human activity, and urban design can all influence how much heat

is absorbed, produced, and retained. Understanding these processes can help cities develop

strategies such as expanding green spaces, planting trees, improving building design, and creating

cooler public areas.

The word ‘simultaneously” in paragraph 4 is closest in meaning to ….

Dari hasil pengamatan Joseph Louis Proust (1754-1826) pada

percobaan-percobaan yang telah dilakukannya, Proust mengemukakan suatu

Postulat. Postulat ini kemudian dikenal dengan hukum perbandingan tetap (hukum

Proust) yang bunyinya : Perbandingan massa unsur-unsur dalam suatu senyawa

adalah tetap.

Unsur Kalsium dan unsur

belerang bersenyawa dalam perbandingan berat 3 : 2 membentuk senyawa kalsium

sulfida. Jika 30 gram kalsium disenyawakan dengan 16 gram belerang maka jawaban

yang

Asam sitrat merupakan salah

satu asam organik yang mempunya banyak manfaat mulai dari bidang makanan,

minuman maupun farmasi. Asam sitrat banyak tersebar dan berasal dari dalam

tumbuhan maupun hewan serta dapat disintesis dengan cara kimiawi maupun biokonversi.

Salah satu metode sintesis yang banyak dikembangkan sekarang adalah biokonversi

dengan fermentasi. Dalam fermentasi terdapat beberapa hal yang dapat

mempengaruhi proses fermentasi yaitu seperti suhu, pH, aerasi, nutrisi dan

sumber karbon. Berikut adalah struktur kimia dari asam sitrat :



Berdasarkan struktur asam

sitrat, berapa persentase massa karbon dalam molekul asam sitrat?

How Heatwaves Become More Dangerous in Cities

A heatwave is a prolonged period of unusually high temperatures that can affect human health,

infrastructure, and natural ecosystems. Although heatwaves can occur in both rural and urban

areas, their effects are often more severe in cities. This happens because several environmental

and human factors interact to increase and retain heat.

One important factor is the concentration of heat-absorbing materials. Urban areas contain large

amounts of concrete, asphalt, and other hard surfaces. During the day, these materials absorb solar

energy and gradually release it after sunset. As a result, buildings, roads, and pavements can remain

warm long after the air temperature begins to decline. This contributes to the urban heat island

effect, in which cities become significantly warmer than surrounding areas.

The lack of vegetation can make the situation worse. Trees and other plants provide shade and

release water vapor through a process called evapotranspiration. This process consumes energy

and helps cool the surrounding environment. When vegetation is replaced by buildings and paved

surfaces, cities lose an important natural cooling mechanism.

Human activities can add even more heat. Vehicles, industrials equipment, and air-conditioning

systems release waste heat into the environment. During an extreme heat event, the increased use

of air conditioners may provide indoor relief but

Urban design can also influence how effectively heat escapes. Closely spaces buildings may

restrict air movement, allowing warm air to remain trapped between structures. Consequently,

some densely developed neighborhoods may experience higher temperatures than areas with more

open spaces and vegetation.

For these reasons, the severity of an urban heatwave is not determined by temperature alone.

Building materials, vegetation, human activity, and urban design can all influence how much heat

is absorbed, produced, and retained. Understanding these processes can help cities develop

strategies such as expanding green spaces, planting trees, improving building design, and creating

cooler public areas.

What is the relationship between air-conditioning and urban heat described in the text?

Чим є кінетична енергія?

How Heatwaves Become More Dangerous in Cities

A heatwave is a prolonged period of unusually high temperatures that can affect human health,

infrastructure, and natural ecosystems. Although heatwaves can occur in both rural and urban

areas, their effects are often more severe in cities. This happens because several environmental

and human factors interact to increase and retain heat.

One important factor is the concentration of heat-absorbing materials. Urban areas contain large

amounts of concrete, asphalt, and other hard surfaces. During the day, these materials absorb solar

energy and gradually release it after sunset. As a result, buildings, roads, and pavements can remain

warm long after the air temperature begins to decline. This contributes to the urban heat island

effect, in which cities become significantly warmer than surrounding areas.

The lack of vegetation can make the situation worse. Trees and other plants provide shade and

release water vapor through a process called evapotranspiration. This process consumes energy

and helps cool the surrounding environment. When vegetation is replaced by buildings and paved

surfaces, cities lose an important natural cooling mechanism.

Human activities can add even more heat. Vehicles, industrials equipment, and air-conditioning

systems release waste heat into the environment. During an extreme heat event, the increased use

of air conditioners may provide indoor relief but

Urban design can also influence how effectively heat escapes. Closely spaces buildings may

restrict air movement, allowing warm air to remain trapped between structures. Consequently,

some densely developed neighborhoods may experience higher temperatures than areas with more

open spaces and vegetation.

For these reasons, the severity of an urban heatwave is not determined by temperature alone.

Building materials, vegetation, human activity, and urban design can all influence how much heat

is absorbed, produced, and retained. Understanding these processes can help cities develop

strategies such as expanding green spaces, planting trees, improving building design, and creating

cooler public areas.

What is the main purpose of the text?

Should School Uniforms be Mandatory?

Whether students should be required to wear school uniforms remains a subject of debate.

Supporters argue that uniforms create equality and strengthen students’ sense of belonging, while

opponents believe that mandatory uniforms can restrict individual expression and create

unnecessary expenses. Therefore, schools need to consider both the advantages and disadvantages

before establishing a uniform policy.

On the one hand, school uniforms can reduce visible differences between students. When everyone

wears similar clothing, students may be less likely to judge one another based on fashion, brands,

or economic background. Uniforms can also create a stronger sense of school identity. Wearing

the same clothing may encourage students to feel that they are part of a shared community rather

than individuals with completely separate identities. In addition, uniforms can make it easier for

school staff to identify students during school activities or when they are outside the classroom.

However, requiring uniforms may limit students’ opportunities to express their personalities

through clothing. Adolescents often use appearance as one way of exploring their identity, and

strict clothing regulations may make some students feel that their individuality is being

unnecessarily restricted. Another concern is cost. Although uniforms are intended to simplify

clothing choices, purchasing several sets of special clothing can be expensive, particularly for

families with more than one school-aged child.

A possible solution is to maintain a basic dress code while allowing students some flexibility.

Schools could require certain standards of neatness and appropriateness without demanding

exactly the same clothing from everyone. Such a policy could preserve order and school identity

while giving students limited opportunities for personal expression.

Ultimately, the decision should depend on the school’s circumstances and priorities. Rather than

treating uniforms as automatically beneficial or harmful, schools should consider equality,

affordability, and students’ need for reasonable self-expression.

The statement “uniforms are intended to simplify clothing choices” implies that uniforms are expected to …..