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Luba_88 [7]
2 years ago
12

I'm giving 20 points! please it's for a friend not me

Chemistry
1 answer:
astra-53 [7]2 years ago
6 0

Answer:

Three chemical elements: hydrogen, oxygen, and helium.

The difference between metals and metalloids is: metalloids have properties in between those of the metals and non-metals and are semiconductors.

The periodic table is organized by the elemts atomic number, it goes from the element with the lowest atomic number (which is hydrogen) to the element with the highest atomic number (oganesson)

Explanation:

Hope this helps :)

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using the following thermochemical equation, determine the amount of heat produced from the combustion of 24.3 g benzene (c6h6).
aliya0001 [1]

the amount of heat produced from the combustion of 24.3 g benzene (c6h6) is ΔH = -976.5 kJ

There are two moles of benzene involved in the process (C6H6). Since the heat of this reaction is -6278 kJ, the burning of 2 moles of benzene will result in a heat loss of 6278 kJ. This reaction is exothermic.

Enthalpy, or the value of H, is a unit of measurement for heat that relies on the amount of matter present (number of moles).

Thus, 24.3 g of benzene contains:

n = mass/molar mass, where n = 24.3/78.11, and n = 0.311 moles.

2 moles = 6278 kJ

0.311 moles =x

By the straightforward direct three rule:

2x = -1953.08 x = -976.5 kJ

Learn more about combustion here-

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4 0
1 year ago
Which statement correctly describes two forms of oxygen, O2 and O3?
fgiga [73]
The two forms of oxygen, O2 and O3 is "<span>They have different molecular structures and different properties."</span>
7 0
3 years ago
Read 2 more answers
Ultraviolet radiation has a frequency of 6.8×1015 Hz. What is the energy associated with this frequency?
stellarik [79]

Use Planck's equation (E=hv) to solve.  where <span>frequency (v) of ultrviolet radiation is 6.8 × 1015 1/s.  </span><span> </span>The variable h is a constant equal to 6.63 × 10-34 J·s
E= <span>(6.8 × 1015 1/s)x(</span>6.63 × 10-34 J·s)


5 0
3 years ago
The first known telescopes, used around 1600, consisted of a lens and an eyepiece. Today, telescopes are often computer controll
Veseljchak [2.6K]

Answer:

B.

Explanation:

The telescopes of the 1600s were gradually improved upon over time, resulting in the telescopes that are available today.

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3 years ago
Which of the following is true about hydropower? It changes the surrounding ecosystem. It does not produce greenhouse gases. It
Whitepunk [10]

Answer:

A

Explanation:

One of the main complaints about hydropower is that it will change the ecosystem. You can read about the history of any dam and you will find that most of them have involved evacuation. That means that farmland was lost and replaced by a lake behind the dam. The energy comes from water cascading over the top of the dam to its bottom.

It does not produce radiation.

It does not burn fossil fuels. It's clean and does not pollute the air.

So there are no greenhouse gases involoved.

3 0
2 years ago
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