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1 year ago

Why is mining for coal a long-term concern?

Chemistry

2 answers:

Free_Kalibri [48]1 year ago

8 0

A. Fossil fuels take a very long time to form so we mine it faster than it can replenish.

maw [93]1 year ago

5 0

Answer: I believe its A

Explanation:

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2) Of the following, which has the shortest de Broglie wavelength? A) an airplane moving at a velocity of 300 mph B) a helium nu

8090 [49]

Answer:

B) a helium nucleus moving at a velocity of 1000 mph

Explanation:

According to the De Broglie relation

λ= h/mv

h= planks constant

m= mass of the body

v= velocity of the body.

As we can see from De Broglie's relation, the wavelength of matter waves depends on its mass and velocity. Hence, a very small mass moving at a very high velocity will have the greatest De Broglie wavelength.

Of all the options given, helium is the smallest matter. A velocity of 1000mph is quite high hence it will have the greatest De Broglie wavelength.

5 0

2 years ago

Tin has ten stable isotopes. The heaviest, 124Sn, makes up 5.80% of naturally occuring tin atoms. How many atoms of 124Sn are pr

matrenka [14]

The average atomic mass of Sn is 118.71 g/mol

the percentage of heaviest Sn is 5.80%

the given mass of Sn is 82g

The total moles of Sn will be = mass / atomic mass = 82/118.71=0.691

Total atoms of Sn in 82g = $6.023X10^{23}X0.691=4.16X10^{23}$

the percentage of heaviest Sn is 5.80%

So the total atoms of $Sn^{124}$ = 5.80% X $4.16X10^{23}$

Total atoms of $Sn^{124}$ = $2.41X10^{22}$ atoms

the mass of $Sn^{124}$ will be = $\frac{2.41X10^{22}X124}{6.023X10^{23}}=4.96g$

5 0

2 years ago

If the initial concentration of NOBr is 0.0440 M, the concentration of NOBr after 9.0 seconds is ________. If the initial concen

Nikolay [14]

This is an incomplete question, here is a complete question.

If the initial concentration of NOBr is 0.0440 M, the concentration of NOBr after 9.0 seconds is ________.

The reaction

$2NOBr(g)\rightarrow 2NO(g)+Br_2(g)$

It is a second-order reaction with a rate constant of 0.80 M⁻¹s⁻¹ at 11 °C.

Answer : The concentration of after 9.0 seconds is, 0.00734 M

Explanation :

The integrated rate law equation for second order reaction follows:

$k=\frac{1}{t}\left (\frac{1}{[A]}-\frac{1}{[A]_o}\right)$

where,

k = rate constant = 0.80 M⁻¹s⁻¹

t = time taken = 142 second

[A] = concentration of substance after time 't' = ?

$[A]_o$ = Initial concentration = 0.0440 M

Putting values in above equation, we get:

$0.80M^{-1}s^{-1}=\frac{1}{142s}\left (\frac{1}{[A]}-\frac{1}{(0.0440M)}\right)$

$[A]=0.00734M$

Hence, the concentration of after 9.0 seconds is, 0.00734 M

5 0

1 year ago

B5H9(l) is a colorless liquid that will explode when exposed to oxygen. How much heat is released when 0.211 mol of B5H9 reacts

n200080 [17]

Answer:

Heat realesed is - 2192.7 kJ

Explanation:

First lets have the chemical equation balanced, and then solve the question based on the fact that the enthalpy change for a reaction is the sum of the enthalpies of formation of products minus reactants.

B₅H₉ (l) + O₂ (g) ⇒ B₂O₃ (s) + H₂O(l)

B atoms we have 5 reactants and 2 products, so the common mltiple is 10 and we have

2 B₅H₉ (l) + O₂ (g) ⇒ 5 B₂O₃ (s) + H₂O(l)

Now balance H by multiplying by 9 the H₂O

2 B₅H₉ (l) + O₂ (g) ⇒ 5 B₂O₃ (s) + 9 H₂O(l)

Finally, balance the O since we have 24 in products by multiplying by 12 the

O₂ ,

2 B₅H₉ (l) + 12 O₂ (g) ⇒ 5 B₂O₃ (s) + 9 H₂O

ΔHrxn = 5 x ΔHºf B₂O₃ + 9 x ΔHºf H₂O - ( 2 x ΔHºf B₅H₉ + 12 x ΔHºf O₂ )

We have all the ΔHºf s except oxygen but remember the enthalpy of formation of a pure element in its standard estate is cero.

ΔHrxn = 5 mol x ( -1272 kJ/mol )+ 9 mol x ( -285.4 kJ/mol ) - ( 2mol x 732 kJ/mol )

= -8928.6 kJ - 1464 kJ = -10,392 kJ

Now this enthalpy change was based in 2 mol reacted according to the balanced equation, so for 0.211 mol of B₅H₉ we will have:

-10,392 kJ/ 2 mol B₅H₉ x 0.211 mol B₅H₉ = - 2192.7 kJ

8 0

1 year ago

Read 2 more answers

Which of the following energy sources obtains its energy from gravitational potential energy?

ipn [44]

It is a geothermal power plant

6 0

1 year ago