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Marat540 [252]
3 years ago
7

How many valence electrons do transition metals have?

Chemistry
1 answer:
alukav5142 [94]3 years ago
4 0
The group/family number is the same number of valance electrons.
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Given the following heats of combustion. CH3OH(l) + 3/2 O2(g) CO2(g) + 2 H2O(l) ΔH°rxn = -726.4 kJ C(graphite) + O2(g) CO2(g) ΔH
sergeinik [125]

Answer:

The standard enthalpy of formation of methanol is, -238.7 kJ/mole

Explanation:

The formation reaction of CH_3OH will be,

C(s)+2H_2(g)+\frac{1}{2}O_2\rightarrow CH_3OH(g),\Delta H_{formation}=?

The intermediate balanced chemical reaction will be,

C(graphite)+O_2(g)\rightarrow CO_2(g), \Delta H_1=-393.5kJ/mole..[1]

H_2(g)+\frac{1}{2}O_2(g)\rightarrow H_2O(l), \Delta H_2=-285.8kJ/mole..[2]

CH_3OH(g)+\frac{3}{2}O_2(g)\rightarrow CO_2(g)+2H_2O(l) , \Delta H_3=-726.4kJ/mole..[3]

Now we will reverse the reaction 3, multiply reaction 2 by 2  then adding all the equations, Using Hess's law:

We get :

C(graphite)+O_2(g)\rightarrow CO_2(g) , \Delta H_1=-393.5kJ/mole..[1]

2H_2(g)+2O_2(g)\rightarrow 2H_2O(l) ,\Delta H_2=2\times (-285.8kJ/mole)=-571.6kJ/mol..[2]

CO_2(g)+2H_2O(l)\rightarrow CH_3OH(g)+\frac{3}{2}O_2(g) ,\Delta H_3=726.4kJ/mole [3]

The expression for enthalpy of formation of C_2H_4 will be,

\Delta H_{formation}=\Delta H_1+2\times \Delta H_2+\Delta H_3

\Delta H=(-393.5kJ/mole)+(-571.6kJ/mole)+(726.4kJ/mole)

\Delta H=-238.7kJ/mole

The standard enthalpy of formation of methanol is, -238.7 kJ/mole

4 0
3 years ago
Which of the following is NOT true of white dwarfs?
liq [111]

Answer:

A white dwarf is what stars like the Sun become after they have exhausted their nuclear fuel. Near the end of its nuclear burning stage, this type of star expels most of its outer material, creating a planetary nebula. Only the hot core of the star remains. ... That means a white dwarf is 200,000 times as dense.

Explanation:

they are cold

they are about the size of Earth

these both are not true

6 0
3 years ago
Read 2 more answers
When cells or organisms maintain a stable internal state in a changing environment is called?
Goryan [66]

Answer:

Homeostasis

Explanation:

8 0
3 years ago
When steam condenses into water, __________. When steam condenses into water, __________. heat is given off by the water no heat
lys-0071 [83]

Answer: heat is given off by the water

Explanation:

Condensation can be defined as the process by which water vapors or steam in the atmosphere are converted into liquid water. It is the part of water cycle. The water form water bodies and terrestrial surfaces gets evaporated in the form of water vapors. These vapors rise in the upper atmospheric layers and aggregate to form the clouds when these vapors become heavy they fall down in the form of rain. Heat is given off in this process by the water vapors or steam to be converted in liquid.

4 0
3 years ago
How did fossil records support the existence of a supercontinent?
alexandr1967 [171]

Answer:

B. Similar fossils were found in different continents.

5 0
3 years ago
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