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IrinaVladis [17]
3 years ago
15

We can also use the equation for enthalpy change for physical phase changes. Consider the phase change H2O(l) → H2O(g). Calculat

e ΔHrxn.
Use ΔHf values from the table above.

ΔHrxn = _____
Chemistry
2 answers:
DIA [1.3K]3 years ago
7 0
Standard molar enthalpy:
H2O ( liquid water ) : - 285.8 KJ/mole
H2O ( water vapor ) : - 241.8 KJ / mole.
ΔHrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0
Answer: B ) 44.0 KJ  
VLD [36.1K]3 years ago
6 0

Answer: The value of enthalpy of the given reaction is 44.000 kJ/mol , that is energy is supplied to water to change into water vapors

Explanation:

H_2O(l)\rightarrow H_2O(g),\Delta H_{rxn}=?

Enthalpy of formation of water in liquid state,\Delta H_{f,H_2O(l)}=-285.820 kJ/mol

Enthalpy of formation of water in gaseous state,\Delta H_{f,H_2O(g)}=-241.820 kJ/mol

\Delta H_{rxn}=\sum \Delta H_f \text{of products}-\sum \Delta H_f \text{of reactants}

\Delta H_{rxn}=(-241.820 kJ/mol)-(-285.820 kJ/mol)=44.000 kJ/mol

The value of enthalpy of the given reaction is 44.000 kJ/mol, that is energy is supplied to water to change into water vapors.

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If 27.3% of a sample of silver-112 decays in 1.52 hours, what is the half-life (in hours to 3 decimal places)?
ICE Princess25 [194]

<u>Answer:</u> The half life of the sample of silver-112 is 3.303 hours.

<u>Explanation:</u>

All radioactive decay processes undergoes first order reaction.

To calculate the rate constant for first order reaction, we use the integrated rate law equation for first order, which is:

k=\frac{2.303}{t}\log \frac{[A_o]}{[A]}

where,

k = rate constant = ?

t = time taken = 1.52 hrs

[A_o] = Initial concentration of reactant = 100 g

[A] = Concentration of reactant left after time 't' = [100 - 27.3] = 72.7 g

Putting values in above equation, we get:

k=\frac{2.303}{1.52hrs}\log \frac{100}{72.7}\\\\k= 0.2098hr^{-1}

To calculate the half life period of first order reaction, we use the equation:

t_{1/2}=\frac{0.693}{k}

where,

t_{1/2} = half life period of first order reaction = ?

k = rate constant = 0.2098hr^{-1}

Putting values in above equation, we get:

t_{1/2}=\frac{0.693}{0.2098hr^{-1}}\\\\t_{1/2}=3.303hrs

Hence, the half life of the sample of silver-112 is 3.303 hours.

6 0
3 years ago
What is the main process by which water moves from land to the atmosphere?
slava [35]

Answer:

isn't that evaporation if not you can just delete my answer-

Explanation:

5 0
3 years ago
Someone please help me!! I'll give brainlest!
Trava [24]

Answer:

Section Three

1. D

2. B

3. A

4. G

5. C

6. F

7. E

Section Four

1. F

2. E

3. B

4. A

5. C

6. D

7. G

Explanation:

4 0
2 years ago
If the atmospheric pressure in the laboratory is 1.2 atm, how many moles of gas were in each syringe? (Hint: Choose one volume a
Naily [24]

Answer:

A: 2.525 x 10-4 mol

B: 2.583 x 10-4 mol

Explanation:

Part A:

Data Given:

. Temperature of water (H2O) = 21.3°C

Convert Temperature to Kelvin

T = °C + 273

T = 21.3 + 273 = 294.3 K

volume of (H2O) gaseous state = 5.1 mL

Convert mL to liter

1000 mL = 1L

5.1 ml = 5.1/1000 = 0.0051 L

Pressure = 1.2 atm

. no. of moles = ?

Solution

no. of moles can be calculated by using ideal gas formula

PV = nRT

Rearrange the equation for no. of moles

n=PV/RT......... (1)

where

P = pressure

V = Volume

T= Temperature

n = Number of moles

R = ideal gas constant

where

R = 0.08206 L.atm/ mol. K

Now put the value in formula (1) to calculate no. of moles of

n = 1.2 atm x 0.0051 L / 0.08206 L.atm.mol-1. K-1 x 294.3 K

n = 0.0061 atm.L / 24.162 L.atm.mol-1

n = 2.525 x 10-4 mol

no. of moles of gas (H2O) = 2.525 x 10-4 mol

Part B:

Data Given:

Temperature of water (H2) = 21.3°C

Convert Temperature to Kelvin

T = "C + 273

T= 21.3 + 273 = 294.3 K

volume of (H2) gas = 5.2 mL

Convert mL to liter

1000 mL = 1 L

5.2 ml = 5.2/1000 = 0.0052 L

Pressure = 1.2 atm

. no. of moles = ?

Solution

no. of moles can be calculated by using ideal gas formula

PV = nRT

Rearrange the equation for no. of moles

n= PV / RT......... (1)

where

P = pressure

V = Volume

T= Temperature

n = Number of moles

R = ideal gas constant

where

R = 0.08206 L.atm/mol. K

Now put the value in formula (1) to calculate no. of moles of

n = 1.2 atm x 0.0052 L/0.08206 L.atm.mol-1. K-1 x 294.3 K

n = 0.0062 atm.L/ 24.162 L.atm.mol-1

n = 2.583 x 10-4 mol

I

no. of moles of gas (H2) = 2.583 x 10-4 mol

8 0
3 years ago
How much states have in united states
Gemiola [76]

Answer:

there are 50 states in the United States

Explanation:

you look at a map and count after that you count Alaska and Hawaii and you have 50

states

8 0
3 years ago
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