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3 years ago

Compare and contrast physical changes with chemical changes.

1 answer:

3 0

There are several differences between a physical and chemical change in matter or substances. A physical change in a substance doesn't change what the substance is. In a chemical change where there is a chemical reaction, a new substance is formed and energy is either given off or absorbed.

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Manganese dioxide (MnO2(s), Hf = –520.0 kJ) reacts with aluminum to form aluminum oxide (AI2O3(s), Hf = –1699.8 kJ/mol) and mang

Temka [501]

Answer : The enthalpy of the reaction = -1839.6 KJ

Solution : Given,

$\Delta (H_{f})_{MnO_{2}}$ = -520.0 KJ/mole

$\Delta (H_{f})_{Al_{2}O_{3}}$ = -1699.8 KJ/mole

The balanced chemical reaction is,

$3MnO_{2}(s)+4Al(s)\rightarrow 2Al_{2}O_{3}(s)+3Mn(s)$

Formula used :

$\Delta (H_{f})_{reaction}=\sum n(\Delta H_{f})_{product}-\sum n(\Delta H_{f})_{reactant}$

$\Delta (H_{f})_{reaction}=(2\times \Delta H_{Al_{2}O_{3}(s)}+3\times \Delta H_{Mn(s)} )-(3\times \Delta H_{MnO_{2}(s) }+4\times\Delta H_{Al}(s))$

We know that the standard enthalpy of formation of the element is equal to Zero.

Therefore, the enthalpy of formation of (Mn) and (Al) is equal to zero.

Now, put all the values in above formula, we get

$\Delta (H_{f})_{reaction}=[2moles\times (-1699.8 KJ/mole)}+3moles\times (0\text{ KJ/mole}})]-[(3moles\times(-520.0KJ/mole }+4moles\times(0\text{ KJ/mole})]$

= (-3399.6) + (1560)

= -1839.6 KJ

5 0

3 years ago

A sample of water at 20 degrees c contains what bonds

vladimir2022 [97]

Covalent and hydrogen bonds

3 0

3 years ago

Calculate the ph of a solution formed by mixing 200.0 ml of 0.30 m hclo with 300.0 ml of 0.20 m kclo. the ka for hclo is 2.9 × 1

masha68 [24]

Answer:

The pH of the solution will be 7.53.

Explanation:

Dissociation constant of KClO= $K_a=2.8\times 10^{-8}$

Concentration of acid in 1 l= 0.30 M

Then in 200 ml = $0.30 M\times 0.200 L=0.06 M$

The concentration of acid, HClO=[acid]= 0.006 M

Concentration of salt in 1 L = 0.20 M

Then in 300 ml = $0.20 M\times 0.300 L=0.06 M$

The concentration of acid, KClO=[salt]= 0.006 M

The pH of the solution will be given by formula :

$pH=pK_{a}^o+\log\frac{[salt]}{[acid]}$

$pH=-\log[2.8\times 10^{-8}]+\frac{[0.06 M]}{[0.06 M]}$

The pH of the solution will be 7.53.

4 0

3 years ago

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sulfur combines with hydrogen to form hydrogen sulfide H2 S by single covalent bond, while it form with potassium by ionic bond

Alex

Answer: Ions may be defined as the element that contains either positive or negative charge over them. Two types of ions are cations and anions. The outermost electrons are involved in the formation of ions.

The atomic number of sulfur is 16. Its outermost electronic configuration is K=2, L= 8, M= 6. The sulfur requres two more electrons to complete its orbit and accquire -2 charge.

Explanation:

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3 years ago

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What is the charge on an atom after it loses an electron during the formation of a bond?

Sphinxa [80]

I believe the charge is positive as losing an electron suggests that the atom lost a negative charge, leaving it with more positive than negative.

I haven't taken this in a few years very sorry if i'm wrong tho.

6 0

3 years ago

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