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3 years ago

An elements atomic number tells you the number of

Chemistry

1 answer:

liq [111]3 years ago

8 0

The number of protons in the nucleus of the atom, I believe. c:

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Physical activity and exercise typically lead to __________.

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<span>Physical activity and exercise typically lead to higher energy levels. As your body gets used to working hard consistently, you tend to be more prepared and in better physical condition. Your body begins to learn that you should burn up calories quickly to prepare to be active, and this results in increased energy levels even when you're not currently exercising.</span>

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3 years ago

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Which of the following is not a characteristic of minerals

PSYCHO15rus [73]

What are the following?

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2 years ago

(Please help!)

Inessa [10]

Answer:

B. temperature decreases as altitude increases.

Explanation:

Just like in the lower reaches of the atmosphere, the troposphere, in the mesosphere, temperature decreases as altitude increases.

The mesosphere is the third layer of the atmosphere just above the stratosphere.

It begins at the top of the stratosphere and ends at the mesopause where the thermosphere begins.
The mesosphere is often referred to as the middle layer.

With increasing height, the temperature of the mesosphere decreases significantly. The top of the mesosphere is one of the coldest part of the earth atmosphere. This is as a result of increasing atmospheric cooling by carbon dioxide in this region of the atmosphere.

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3 years ago

An alloy is a mixture that has

defon

Answer:

an alloy is a mixture of elements that has metallic properties

Explanation:

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2 years ago

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Calculate the enthalpy of the reaction

harkovskaia [24]

Answer : The enthalpy of the reaction is, -2552 kJ/mole

Explanation :

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.

The given enthalpy of reaction is,

$4B(s)+3O_2(g)\rightarrow 2B_2O_3(s)$ $\Delta H=?$

The intermediate balanced chemical reactions are:

(1) $B_2O_3(s)+3H_2O(g)\rightarrow 3O_2(g)+B_2H_6(g)$ $\Delta H_A=+2035kJ$

(2) $2B(s)+3H_2(g)\rightarrow B_2H_6(g)$ $\Delta H_B=+36kJ$

(3) $H_2(g)+\frac{1}{2}O_2(g)\rightarrow H_2O(l)$ $\Delta H_C=-285kJ$

(4) $H_2O(l)\rightarrow H_2O(g)$ $\Delta H_D=+44kJ$

Now we have to revere the reactions 1 and multiple by 2, revere the reactions 3, 4 and multiple by 2 and multiply the reaction 2 by 2 and then adding all the equations, we get :

(when we are reversing the reaction then the sign of the enthalpy change will be change.)

The expression for enthalpy of the reaction will be,

$\Delta H=-2\times \Delta H_A+2\times \Delta H_B-6\times \Delta H_C-6\times \Delta H_D$

$\Delta H=-2(+2035kJ)+2(+36kJ)-6(-285kJ)-6(+44)$

$\Delta H=-2552kJ$

Therefore, the enthalpy of the reaction is, -2552 kJ/mole

4 0

3 years ago