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Marianna [84]
3 years ago
10

Ammonium nitrate is an ingredient in cold packs used by sports trainers for injured athletes. Calculate the change in temperatur

e when 42 g of ammonium nitrate (NH&NOs, 80.1 g/mol) dissolves in 250 g water. Assume the specific heat of the solution is 4.18 J/(g °C). NH4NO3(s)-> NH4"(aq) + NO3-(aq) ΔΗ-25.7 kJ/mol
Chemistry
1 answer:
Ronch [10]3 years ago
3 0

Answer:

See explanation

Explanation:

First, we need to use the correct expression:

Q = m*Cp*ΔT  (1)

Q = n*ΔH  (2)

These are the 2 expressions to calculate heat or energy.

Now, we want to know the change of temperature of the nitrate in water after being added, so with the innitial data of nitrate, we can calculate heat using the second expression. First, we need to calculate moles with the molecular mass:

n = m/MM

n = 42/80.1 = 0.52 moles

With these moles, we can calculate heat with the ΔH of this reaction:

Q = 0.52 * 25.7 = 13.364 kJ or 13,364 J

However, this heat as is being absorbed, the value would be negative.

Now that we have heat, we can use expression (1) and plug these values to solve for ΔT, but before, we need to know the total mass of the solution (water + nitrate)

m = 250 + 42 = 292 g

now, solving for ΔT:

-13,364 = 292 * 4.18 * ΔT

ΔT = -13,363 / (292 * 4.18)

ΔT = -10.95 °C

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Calculate the mass of beryllium (Be) needed to completely react with 18.9 g nitrogen gas (N2) to produce Bez N2, which is the on
choli [55]

Answer:

C = 18.29 g  

Explanation:

Given data:

Mass of beryllium needed = ?

Mass of nitrogen = 18.9 g

Solution:

Chemical equation:

3Be + N₂    →    Be₃N₂

now we will calculate the number of moles of nitrogen:

Number of moles = mass/molar mass

Number of moles = 18.9 g/ 28 g/mol

Number of moles = 0.675 mol

Now we will compare the moles of nitrogen and Be from balance chemical equation.

                     N₂        :       Be        

                       1          :       3

                  0.675       :      3/1×0.675 = 2.03 mol

Number of moles of Be needed are 2.03 mol.

Mass of Beryllium:

Mass = number of moles × molar mass

Mass = 2.03 mol ×   9.01 g/mol

Mass = 18.29 g  

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3 years ago
HELP ME!!<br> How many people prefer pepperoni or tomato as a topping?
Vadim26 [7]

Answer:

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The postulate of Dalton's atomic theory that atom is indivisible particle and can be subdivided into smaller particles was later changed because atom can be divided into neutrons, protons and electrons. It was changed because after later finding out that the atom can be divided, the theory was changed to the correct finalized theory.

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Using the periodic table entry of iron below, match the numbers with what they represent.
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Answer:

Answers:

1. The number 26 ↔ atomic number

2. The number 56 ↔ mass number

3. The number 4 ↔ the number of orbits

4. The number 30 ↔ number of neutrons.

5. The number 14 ↔ number of electrons in n = 3

6. The number 2 ↔ number of valence electrons.

Explanation:

The same relevant information to deal with the data reported can be found in many periodic tables.

Herewith, I copy the mentioned entry. Please see the image attached.

This is the explanation of the information shown in the entry:

1) Symbol: in the centre of the picture: Fe. It is the symbol of iron.

2) Superscript to the lef of the symbol: 26. It is the atomic number, i.e. the number of protons. Hence, this is the first match:

         1. The number 26 ↔ atomic number

3) The number 55.845 below the symbol and name of the element is the atomic mass of the element.

The atomic mass is the avereage mass of the several isotopes of the same element that exist in nature.

The particles that count for the atomic mass are the neutrons and protons, and that is reason of the called mass number, which is the sum of the neutrons and protons of a particular isotope.

An atomic mass of 55.845 means that likely there exist isotopes with mass number 56. This is, with a total number of 56 nucleons (protons and neutrons).

Since, as explained above, Fe has 26 protons, you can calcualte the number of neutrons of the 56 mass number isotope as: n = 56 - 26 = 30 neutrons.

Hence, you can match these:

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        4. The number 30 ↔ number of neutrons

5. The numbers 2, 8, 14, and 2, that appear in the upper right corner of the image are the number of electrons in the different main energy levels, which is the principal quantum number (n)

They mean:

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 1                               2

2                               8

3                              14

4                             2

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5. The number 14 ↔ number of electrons in n = 3

6. The number 2 ↔ number of valence electrons

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3. The number 4 ↔ the number of orbits

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