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3 years ago

All elements are pure substances. True False

1 answer:

5 0

It can be a compound or a single element. An element is a pure substance that cannot be separated into simpler substances by chemical or physical means. There are about 117 elements, but carbon, hydrogen, nitrogen and oxygen are only a few that make up the largest portion of Earth.
hopefully that helps

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How many moles are in 281 g of Ca(OH)2?

Natasha_Volkova [10]

Answer:

3.79 moles

Explanation:

To convert moles to gams of a substance we need to find the molar mass of the substance. For Ca(OH)₂ th molar mass is:

1Ca = 40.08g/mol

2O = 2*16g/mol = 32g/mol

2H = 2*1.01g/mol = 2.02g/mol

The molar mass is:

40.08g/mol + 32g/mol + 2.02g/mol = <em>74.1g/mol</em>

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And moles are:

281g * (1mol / 74.1g) =

<h3>3.79 moles</h3>

5 0

2 years ago

Consider an atom having four distinct energy levels. If an electron is able to make transitions between any two levels, how many

Kryger [21]

Energy levels are the electron shells where electrons are found at a fixed distance from the nucleus of the atom. The atom could emit 6 different wavelengths.

<h3>What is wavelength?</h3>

A wavelength is a distance between the adjacent crests in wave signals propagated in a system. Wavelength $(\rm \lambda )$ is in inverse relation to the frequency of the wave.

When an electron jumps from energy level 1 to 2, 1 to 3, and 1 to 4 one wavelength each is present. Hence, making the total wavelength to be 3, in transition from the first energy level.

Similarly, from energy levels, 2 to 3 and 2 to 4, a total of 2 wavelengths, and from energy levels 3 to 4 one wavelength is produced.

So the total different wavelengths of the radiation that can be emitted will be 3 + 2 + 1 = 6.

Therefore, 6 different wavelengths of radiation will be emitted by the atom.

Learn more about wavelengths here:

brainly.com/question/21419520

#SPJ1

7 0

1 year ago

If 1.3 L of C3H8 combusts according to the equation below, how much CO2 will be produced?

SCORPION-xisa [38]

Answer:

0.162 moles of CO₂ are produced by this reaction

Explanation:

The reaction is:

C₃H₈(g) + 5O₂(g) → 3CO₂(g) +4H₂O(g)

As we have the volume of propane, we need to know the mass that has reacted, so we apply density's concept.

Density = Mass / Volume → Density . Volume = Mass

0.00183 g/mL . 1300 mL = Mass → 2.379 g

We determine the moles → 2.379 g . 1mol / 44 g = 0.054 moles

Ratio is 1:3. 1 mol of propane can produce 3 moles of dioxide

Then, 0.054 moles may produce (0.054 .3)/1 = 0.162 moles

6 0

3 years ago

1. How much 6.0 M HNO3 is needed to neutralize 39 mL of 2.0 M KOH?

quester [9]

Answer:

For 2. the answer is 15.0 mL

For other examples, you can solve by exact way as I have solved the 2nd example.

I have writen down all the balanced chemical reaction equation for examples 1, 3, 4, 5 for you. ( picture 2 )

Explanation:

Please see the step-by-step solution in the picture attached below.(picture 1)

Hope this answer can help you. Have a nice day!

6 0

3 years ago

Select the item(s) that are organs in either a plant or human

Nataly_w [17]

Plant: leaf tissue
Human: lungs

3 0

3 years ago