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4 years ago

How does radioactivity make it possible to understand how earth can be so old and still have a hot interior?

2 answers:

8 0

I know that we can find how old the Earth is by knowing how much uranium ultimately decayed into lead. Uranium-238 has a very long to decay, about 4.5 billion years. So that is how we are able to understand how old the Earth is.

Sophie [7]4 years ago

4 0

Answer:

The reason is that there are radioactive elements that are in the center of the earth.

Explanation:

If the earth were only a rock cooling from the time of its birth. It should have already cooled completely thousands of years ago. However, volcanoes continue to shed hot magma and this is proof that there is a source of heat in the center of the earth. This source of heat is due to the radioactivity of elements such as Uranium and Thorium that were enclosed during the formation of the earth. These elements slowly disintegrate emitting particles that collide with others emanating heat. For example, the half-life of uranium is 4.5 billion years, which means that it decays very slowly.

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The name given to the main group elements in group 2 is _______.

navik [9.2K]

Answer:

Alkaline Earth Metals

3 0

3 years ago

A substance has a triple point at −24.5 ∘C and 225 mmHg. What is most likely to happen to a solid sample of the substance as it

mr Goodwill [35]

Answer:

The solid will sublime into a gas

Explanation:

In the graph in the attachment

Y-axis represents pressure in mm of Hg

X- axis represents temperature in degree Celsius

The graph show the triple point of water.

Clearly, the sample will go from solid to vapor directly, no liquid involved (pink line is there to show that this is below triple point)

expect sublimation

The solid will sublime into a gas.

4 0

3 years ago

When 78.6 g of urea CH4N2O are dissolved in 700. g of a certain mystery liquid X, the freezing point of the solution is 4.9 Â°C

iogann1982 [59]

Answer:

The van't Hoff factor of NaCl in liquid X is 1.69

Explanation:

Step 1: Data given

Mass of urea = 78.6 grams

Molar mass of urea = 60.06 g/mol

Mass of liquid X = 700 grams = 0.700 kg

he freezing point of the solution is 4.9°C lower than the freezing point of pure X

When 78.6 g of sodium chloride are dissolved in the same mass of X, the freezing point of the solution is 8.5°C lower than the freezing point of pure X.

Molar mass of NaCl = 58.44 g/mol

Step 2: Calculate moles

Moles urea = mass / molar mass

Moles urea = 78.6 grams / 60.06 g/mol

Moles urea = 1.31 moles

Moles NaCl = 78.9 grams / 58.44 g/mol

Moles NaCl = 1.35 moles

Step 3: Calculate molality

Molality = moles / mass of liquid

Molality urea = 1.31 moles / 0.700 kg

Molality = 1.87 molal

Molality NaCl = 1.35 moles / 0.700 kg

Molality NaCl = 1.92 molal

Step 4: Calculate the freezing point depression constant of X

ΔT = i*Kf*m

⇒with ΔT = the freezing point depression = 4.9 °C

⇒with i = the van't hoff factor of urea = 1

⇒with Kf =the freezing point depression consant of X = TO BE DETERMINED

⇒with m = the molality of urea solution = 1.87 molal

4.9 °C = 1 * Kf * 1.87 molal

Kf == 4.9 / 1.87

Kf = 2.62 °C/m

Step 5: Calculate the van't Hoff facotr of NaCl in X

ΔT = i*Kf*m

⇒with ΔT = the freezing point depression = 8.5 °C

⇒with i = the van't hoff factor of urea = TO BE DETERMINED

⇒with Kf =the freezing point depression consant of X = 2.62 °C/m

⇒with m = the molality of urea solution = 1.92 molal

8.5 °C = i * 2.62 °C/m * 1.92 m

i = 8.5 / (2.62 * 1.92)

i = 1.69

The van't Hoff factor of NaCl in liquid X is 1.69

5 0

3 years ago

Determine the bond order from the molecular electron configurations. ( σ 1 s ) 2 ( σ 1 s * ) 2 ( σ 2 s ) 2 ( σ 2 s * ) 2 ( σ 2 p

almond37 [142]

Explanation:

The bond order is defined as number of electron pairs present in a bond of the two atoms.

The formula of bond order is given by:

= $\frac{1}{2}\times (\text{Number of bonding electrons}-\text{Number of anti-bonding electrons})$

1) $(\sigma 1 s )^2 ( \sigma 1 s*)^2 (\sigma 2s )^2 ( \sigma 2 s*)^2 ( \sigma 2 p )^2 ( \pi2 p )^4 (\pi 2 p *)^2$

Number of bonding electrons = 10

Number of anti-bonding electrons = 6

The bond order : $\frac{1}{2}\times (10-6)=2$

2) $( \sigma 1 s )^2 ( \sigma 1 s * )^2 ( \sigma 2 s )^2$

Number of bonding electrons = 4

Number of anti-bonding electrons = 2

The bond order : $\frac{1}{2}\times (4-2)=1$

8 0

3 years ago

2Al(S)+1.5O2(S)→Al2O3(s) H= -1676.0 KJ

mestny [16]

Answer:

$∆H = - 1676.0 - 0 \\ = - 1676.0 \\ heat \: gained \: in \: reaction \: of \: iron \: and \: oxygen \: is \: zero \: because \: it \: is \: not \: given$

5 0

3 years ago