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Hitman42 [59]
3 years ago
6

Standard Thermodynamic Quantities for Selected Substances at 25 ∘C Reactant or product ΔHf∘(kJ/mol) Al(s) 0.0 MnO2(s) −520.0 Al2

O3(s) −1675.7 Mn(s) 0.0 Part A The thermite reaction, in which powdered aluminum reacts with manganese oxide, is highly exothermic. 4Al(s)+3MnO2(s)→2Al2O3(s)+3Mn(s) Use standard enthalpies of formation to find ΔH∘rxn for the thermite reaction.
Chemistry
1 answer:
Svet_ta [14]3 years ago
4 0

Answer:

-1815.4 kJ/mol

Explanation:

Starting with standard enthalpies of formation you can calculate the standard enthalpy for the reaction doing this simple calculation:

∑ n *ΔH formation (products) - ∑ n *ΔH formation (reagents)

This is possible because enthalpy is state function meaning it only deppends on the initial and final state of the system (That's why is also possible to "mix" reactions with Hess Law to determine the enthalpy of a new reaction). Also the enthalpy of formation is the heat required to form the compound from pure elements, then products are just atoms of reagents organized in a different form.

In this case:

ΔH rxn = [(2 * -1675.7) - (3 * -520.0)] kJ/mol = -1815.4 kJ/mol

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How many neutrons and protons are there in the nuclei of the following atoms. a. Li-7 b. O-16 c. Th-232 d. Pu-239
ANEK [815]

Answer:

a.

P = 3 , N = 4

b.

P = 8 , N = 8

c.

P = 90 , N = 142

d.

P = 94 , N = 145

Explanation:

Mass number  = Number of protons + Number of neutrons

Also,

Atomic number = Number of protons

<u>Li - 7</u>

Given, Mass number of Lithium = 7

For lithium, atomic number = 3

So,

Number of protons = 3

Number of neutrons = Mass number - Number of protons = 7 - 3 = 4

<u>O - 16</u>

Given, Mass number of oxygen = 16

For oxygen, atomic number = 8

So,

Number of protons = 8

Number of neutrons = Mass number - Number of protons = 16 - 8 = 8

<u>Th - 232</u>

Given, Mass number of Thorium = 232

For Thorium, atomic number = 90

So,

Number of protons = 90

Number of neutrons = Mass number - Number of protons = 232 - 90 = 142

<u>Pu - 239</u>

Given, Mass number of Plutonium = 239

For Plutonium, atomic number = 94

So,

Number of protons = 94

Number of neutrons = Mass number - Number of protons = 239 - 94 = 145

3 0
3 years ago
Superstition or science
Nesterboy [21]

Answer:

superstition

Explanation:

Because there is no scientific reason behind it and no connection of it to science.

3 0
3 years ago
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butalik [34]
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7 0
2 years ago
2.5 piece of lithium is dropped into a 500 g sample of water at 22.1 C.ten temperature of the water increases to 23.5 C. How muc
Dominik [7]

Answer:

2.6 kJ  

Explanation:

The formula for the amount of heat (q) absorbed by the water is

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2. Calculate q

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3 years ago
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Ede4ka [16]
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