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solniwko [45]
4 years ago
14

Why can't chemical changes be undone? Because of the chemical properties. Because Mark is an idiot. Because they need energy. Be

cause new substances are formed.
Chemistry
1 answer:
Volgvan4 years ago
8 0

Answer: Because new substances are formed.

Explanation: A chemical property is any of a material's properties that becomes evident during, or after, a chemical reaction; that is, any quality that can be established only by changing a substance's chemical identity.  Once a chemical change occurs it cannot be undone due to the change in chemical identity.  The creation of a new substance is not reversible.  

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HELP 20 POINTS <br>A photon has a wavelength of 366 nm. What is the frequency of this photon?​
den301095 [7]

Answer:

9.  8.2x10¹⁴ Hz

Explanation:

Wavelength λ = 366 nm

Formula: Frequency = C / λ

To find the wavelength in m,

1 nm = 1.0x10⁻⁹ m

So, 366 nm = ?

= 3.66x10⁻⁷ m

Frequency = 3.0x10⁸m.s-1 / 3.66x10⁻⁷ m

                  = 8.2x10¹⁴ s-1

8 0
3 years ago
Water molecules are polar because the?
disa [49]

Answer:

Water (H2O) is polar due to the  bent shape of the molecule. The shape means most of the negative charge from the oxygen is one one side of the molecule and the positive charge of the hydrogen atoms is on the other side of the molecule. This is an example of polar covalent chemical bonding.

Hope this helps!

6 0
3 years ago
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Write a word equation for the chemical reaction.<br><br> I’ll brainlist.
Alex

Answer:

potassium hydroxide + sulfuric acid → potassium sulfate + water.

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5 0
3 years ago
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
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