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Nostrana [21]
3 years ago
15

Va rog ! urgent! E pt chimie ​

Chemistry
1 answer:
n200080 [17]3 years ago
5 0

Answer:

An element

It stays shiny

Explanation:

Pure Gold is an element.

An element is a distinct substance that cannot be split-up into simpler substances. Such substances consists of only one kind of atom.

There are over a hundred elements known to date.

As an element, Gold is classified as a metal due to its very unique set of properties.

One of the indicator that gold does not react with oxygen is that it stays shiny. It does not give rusty look when exposed to air.

Substances that combines with oxygen have a rusty look or change appearance when expose to air. For example, iron.

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In 3–5 sentences, explain the various factors that should be considered when implementing green roofs
Kruka [31]

Answer:

you should consider waterproofing. depending on the climate in your area, you need to apply multiple layers of waterproofing in the roof for it to support vegetation. you should also confused the types of plants. the types of plants is important for the success of your roof. if you live in a dry area, you don't want to choose plants that can live in dry areas without drying out.

6 0
3 years ago
Why do farmers spray water over their crops before a frost?
Nezavi [6.7K]

Answer:

When water freezes and turns into ice, it releases latent heat. Then, the ice that builds up on the plant will insulate it from the colder surrounding air temperatures. Because of this, some growers choose to spray their crop with water before the freeze occurs.

Explanation:

5 0
3 years ago
CaO + H2O -> Ca(OH)2
yawa3891 [41]

The % yield of Ca(OH)₂ : 62.98%

<h3>Further eplanation </h3>

Percent yield is the compare of the amount of product obtained from a reaction with the amount you calculated

General formula:

Percent yield = (Actual yield / theoretical yield )x 100%

An actual yield is the amount of product actually produced by the reaction. A theoretical yield is the amount of product that you calculate from the reaction equation according to the product and reactant coefficients

Reaction

CaO + H₂O ⇒ Ca(OH)₂

mass CaO= 4.2 g

mol CaO(MW=56,0774 g/mol) :

\tt mol=\dfrac{mass}{MW}\\\\mol=\dfrac{4.2}{56,0774 g/mol}\\\\mol=0.075

mol Ca(OH)₂ based on mol CaO

mol ratio CaO : Ca(OH)₂,= 1 : 1, so mol Ca(OH)₂ = 0.075

mass Ca(OH)₂(MW=74,093 g/mol) ⇒ theoretical

\tt mass=mol\times MW\\\\mass=0.075\times 74,093 g/mol\\\\mass=5.557~g

% yield :

\tt =\dfrac{actual}{theoretical}\times 100\%\\\\=\dfrac{3.5}{5.557}\times 100\%\\\\=62.98\%

8 0
2 years ago
What causes different colors to appear in the sky?
katrin [286]

Answer:

Molecules and small particles in the atmosphere change the direction of light rays, causing them to scatter. Scattering affects the color of light coming from the sky.

Explanation:

3 0
3 years ago
Select the word or phrase that best completes each of the following sentences.
harina [27]

Answer:

1. Cells

2. Molecules

3. Organ

3 0
3 years ago
Read 2 more answers
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