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julsineya [31]
3 years ago
8

Describe three signs that a chemical reaction has taken place and give an example of each sign

Chemistry
1 answer:
il63 [147K]3 years ago
7 0
Color change, temperature change, bubbling, state change

green to blue, hot to cold, bubbles (lol), and liquid to gas
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Read the descriptions below of two substances and an experiment on each. Decide whether the result of the experiment tells you t
marissa [1.9K]

Answer:

Sample A is a mixture

Sample B is a mixture

Explanation:

For sample A, we are told that the originally yellow solid was dissolved and we obtained an orange powder at the bottom of the beaker. Subsequently, only about 30.0 g of solid was recovered out of the 50.0g of solid dissolved. This implies that the solid is not pure and must be a mixture. The other components of the mixture must have remained in solution accounting for the loss in mass of solid obtained.

For sample B, we are told that boiling started at 66.2°C and continued until 76.0°C. The implication of this is that B must be a mixture since it boils over a range of temperatures. Pure substances have a sharp boiling point.

7 0
2 years ago
Mengapa garam NaNO2 dapat membirukan kertas lakmus merah? Jelaskan dengan reaksi kimianya!
Reika [66]
Can't understand this. English Please!  :) :)
8 0
3 years ago
An unknown liquid is composed of 34.31% c, 5.28% h, and 60.41% i. The molecular weight is 210.06 amu. What is the molecular form
ozzi

In an unknown liquid, the percentage composition with respect to carbon, hydrogen and iodine is 34.31%, 5.28% and 60.41% respectively.

Let the mass of liquid be 100 g thus, mass of carbon, hydrogen and oxygen will be 34.31 g, 5.28 g and 60.41 g respectively.

To calculate molecular formula of compound, convert mass into number of moles as follows:

n=\frac{m}{M}

Molar mass of carbon, hydrogen and iodine is 12 g/mol, 1 g/mol and 126.90 g/mol.

Taking the ratio:

C:H:I=n_{C}:n_{H}:n_{I}

Putting the values,

C:H:I=\frac{34.31 g}{12 g/mol}:\frac{5.28 g}{1 g/mol}:\frac{60.41 g}{126.90 g/mol}=6:11:1

Thus, molecular formula of compound will be C_{6}H_{11}I.

4 0
3 years ago
How does classifying the components of air help us to solve the air quality crisis
Lubov Fominskaja [6]

Air pollution is

1. Coal

Herder and Sheep in Central Java. © Kemal Jufri / Greenpeace

A shepherdess watches over her flock of sheep that graze near a coal power plant in Jepara, Central Java, Indonesia. © Kemal Jufri / Greenpeace

Burning all fossil fuels is bad, but coal is the worst. When burnt, it releases more carbon dioxide (CO2) per unit of energy than oil or gas – which means it heats up our planet faster.

Coal is toxic too. Burning it releases elements like mercury and arsenic, and small particles of soot which contribute to air pollution. When we breathe it in, that soot harms our heart and lungs and even increases our risk of strokes.

But the worst thing about coal is how widespread it is. Coal provides more than a third of the world’s electricity. That’s more than any other single source! These power plants affect air quality for hundreds of kilometres – and are often placed right in the heart of cities – so countless millions of people get little respite from the pollution these plants cause.

We desperately need to wean ourselves off coal, and get our power from clean sources like wind, sun and tides.

Some counties have started. In 2019, coal power had its biggest slump ever recorded! But we need every country in the world to move much faster towards renewable energy. Greenpeace International has even mapped out how they could go about

Air pollution is indeed a crisis, but it’s a crisis we can solve – and around the world, people are solving it! Here’s what that looks like.

1. Coal

Coal is toxic too. Burning it releases elements like mercury and arsenic, and small particles of soot which contribute to air pollution. When we breathe it in, that soot harms our heart and lungs and even increases our risk of strokes.

But the worst thing about coal is how widespread it is. Coal provides more than a third of the world’s electricity. That’s more than any other single source! These power plants affect air quality for hundreds of kilometres – and are often placed right in the heart of cities – so countless millions of people get little respite from the pollution these plants cause.

We desperately need to wean ourselves off coal, and get our power from clean sources like wind, sun and tides

2. Cars

Most cars run on oil – petrol and diesel. And just like burning coal, burning oil comes with a huge environmental price tag. Petrol and diesel cars emit CO2 and other gases which heat our planet. On top of other nasties, the exhaust fumes these cars produce contain Nitrogen Dioxide (NO2), which is another pollutant that harms our health.

Cities around the world are waking up to the joys of car-free travel. From pedestrian zones, to proper public infrastructure to comprehensive and affordable public transport, there are so many ways cities can help us go car-free more often. And the benefits are many – from more space and cleaner air to a more active and healthy population.

But for those journeys that still need cars, we should start thinking about cars very differently. Rather than petrol and diesel, we should power cars with electricity.

3. Air pollution is no match for all of us, working together. All the solutions listed here are already happening around the world because people came together and demanded it.

Concerns about air pollution made Shenzhen, China electrify their bus fleet. Parents in Belgium mobilised because the air in schools was so dirty. Now, Brussels, its capital city, is banning petrol and diesel cars from 2030 and investing in public transport and cycling infrastructure. And around the world, concerns about the climate impacts of coal are causing governments to look into new ways of getting their power- Turkey has closed five coal power plants in 2020 alone!

4 0
3 years ago
Hydrofluoric acid, hf(aq), cannot be stored in glass bottles because compounds called silicates in the glass are attacked by the
Trava [24]
1) Chemical equation

Na2 SiO3 (s) + 8 HF (aq) ---> H2 Si F6 (aq) + 2 Na F (aq) + 3H2O (l)

It is balanced

2) Molar ratios

1 mol Na2 SiO3 : 8 mol HF.

3) Proportion

0.340 mol Na2 SiO3 * 8 mol HF / 1mol Na2SiO3 = 2.72 mol HF.

Answer: 2.72 mol HF

5 0
3 years ago
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