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Oksi-84 [34.3K]
3 years ago
13

Instant cold packs used to ice athletic injuries on the field contain ammonium nitrate and water separated by a thin plastic div

ider. When the divider is broken, the ammonium nitrate dissolves according to the endothermic reaction: NH4NO3(s) → NH+4(aq) + NO−3(aq) In order to measure the enthalpy change for this reaction, 2.25 g of NH4NO3 is dissolved in enough water to make 15.0 mL of solution. The initial temperature is 25.8 oC and the final temperature (after the solid dissolves) is 21.9 oC. Calculate the change in enthalpy for the reaction in kJ. (Use 1.0 g/mL as the density of the solution and 4.18 J/g . oC as the specific heat capacity.)
Chemistry
1 answer:
Jlenok [28]3 years ago
5 0

Answer:

8.693kJ

Explanation:

The enthalpy change of a reaction is the heat produced per mole of reaction.

For the reaction:

NH₄NO₃(s) → NH₄⁺(aq) + NO₃⁻(aq)

The heat produced (Using coffe cup calorimeter formula) is:

Q = - m×C×ΔT

<em>Where Q is heat, m is mass of solution (15.0mL ≡ 15.0g -Density of 1g/mL), C is specific heat capacity of solution (4.18J/g°C) and ΔT is change in temperature (21.9°C - 25.8°C = -3.9°C).</em>

<em />

Replacing:

Q = -15.0g×4.18J/g°C×-3.9°C

Q = 244.5J is heat of reaction per 2.25g of NH₄NO₃.

Moles in 2.25g of NH₄NO₃ -80.0g/mol-:

2.25g × (1mol / 80.0g) = 0.0281 moles of NH₄NO₃

Thus, enthalpy change of reaction is:

244.5J / 0.0281mol = 8693J = <em>8.693kJ</em>

<em />

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If two metals both have the same color, have similar densities, and are about the same size, but one is shiny and the other is d
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3 years ago
A compound made of elements A and B, has a cubic unit cell. There is an A atom at each corner of the cube and an A atom at the c
Lorico [155]

Answer:

A₅B₄

Explanation:

Since we have one atom of element A at the center of each face of the unit cell, since the unit cell is a cubic cell, we have 6 faces. Since the atom on the face of the unit cell is shared with another cell, we have half of it in the unit cell is shared So, the number of atoms per face is 1/2 atom/face × 6 faces = 4 atoms on the faces of the unit cell.

Also, we have 1 atom at each corner of the cubic unit cell. Since there are 8 corner in the cubic unit cell. Also, each atom at the corner is shared with 8 unit cells, so we have 1/8 atom per corner. So, the number of atoms per unit cell is 1/8 atom/corner × 8 corners = 1 atoms at the corners of the unit cell.

So, in total we have 4 + 1 = 5 atoms of element A in the unit cell.

Also, there are 4 atoms of element B in the unit cell.

So, the ratio of atoms of element A to element B is 5 : 4.

A:B = 5:4

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Gasoline and motor oil are chemically similar. They are both mixtures of nonpolar hydrocarbons containing carbon and hydrogen at
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4 0
3 years ago
Read 2 more answers
Which element is more likely to dissociate into its monatomic form at 3000 K. H or N. Why?
Oliga [24]

Answer:

H2

Explanation:

In the first place it is necessary to consider that these two elements will be their diatomic form initially, that is, H2 and N2.

first we should check the equilibrium constant Kp tables in this case at a temperature of 3000K

Value for dissociation reaction of H2  in Kp = -3.685

Value for dissociation reaction of N2 in Kp = -22.359

Equilibrium constant for H2 dissociation is higher than N2 dissociation. so for this comparation H2 is more likely to dissociate.

8 0
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