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kondor19780726 [428]
3 years ago
9

Has boiling vents in the datk door

Chemistry
1 answer:
77julia77 [94]3 years ago
8 0

Marine.

Hope this helps!

-Payshence

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Calculate the standard enthalpy change for the reaction at 25 ∘ 25 ∘ C. Standard enthalpy of formation values can be found in th
WINSTONCH [101]

<u>Answer:</u> The standard enthalpy change of the reaction is coming out to be -16.3 kJ

<u>Explanation:</u>

Enthalpy change is defined as the difference in enthalpies of all the product and the reactants each multiplied with their respective number of moles. It is represented as \Delta H

The equation used to calculate enthalpy change is of a reaction is:  

\Delta H_{rxn}=\sum [n\times \Delta H_f(product)]-\sum [n\times \Delta H_f(reactant)]

For the given chemical reaction:

Mg(OH)_2(s)+2HCl(g)\rightarrow MgCl_2(s)+2H_2O(g)

The equation for the enthalpy change of the above reaction is:

\Delta H_{rxn}=[(1\times \Delta H_f_{(MgCl_2(s))})+(2\times \Delta H_f_{(H_2O(g))})]-[(1\times \Delta H_f_{(Mg(OH)_2(s))})+(2\times \Delta H_f_{(HCl(g))})]

We are given:

\Delta H_f_{(Mg(OH)_2(s))}=-924.5kJ/mol\\\Delta H_f_{(HCl(g))}=-92.30kJ/mol\\\Delta H_f_{(MgCl_2(s))}=-641.8kJ/mol\\\Delta H_f_{(H_2O(g))}=-241.8kJ/mol

Putting values in above equation, we get:

\Delta H_{rxn}=[(1\times (-641.8))+(2\times (-241.8))]-[(1\times (-924.5))+(2\times (-92.30))]\\\\\Delta H_{rxn}=-16.3kJ

Hence, the standard enthalpy change of the reaction is coming out to be -16.3 kJ

6 0
3 years ago
The half-life for beta decay of strontium-90 is 28.8 years. a milk sample is found to contain 10.3 ppm strontium-90. how many ye
ryzh [129]

Answer : The correct answer is 96.68 yrs

Radioactivity Decay :

it is a process in which a nucleus of unstable atom emit energy in form of radiations like alpha particle , beta particle etc .

Radioactive decay follows first order kinetics , so its rate , rate constant , amount o isotopes can be calculated using first order equations .

The first order equation for radioactive decay can be expressed as :

ln \frac{N}{N_0}  = - k*t ----------- equation (1)

Where : N = amount of radioisotope after time "t"

N₀ = Initial amount of radioisotope

k = decay constant and t = time

Following steps can be used to find time :

1) To find deacy constant :

Decay constant can be calculated using half life . Decay constant and half life can be related as :

T _\frac{1}{2} = \frac{ln2}{k} ---------equation (2)

Given : Half life of Strontium -90 = 28.8 years

Plugging value of T_\frac{1}{2} in above formula (equation 2) :

28.8 yrs = \frac{ln 2}{ k }

Multiply both side by k

28.8 yrs * k = \frac{ln 2 }{k} * k

Dividing both side by 28.8 yrs

\frac{28.8 yrs * k}{28.8 yrs} = \frac{ln 2}{28.8 yrs}

(ln 2 = 0.693 )

k = 0.0241 yrs⁻¹

Step 2 : To find time :

Given : N₀ = 10.3 ppm N = 1.0 ppm k = 0.0241 yrs⁻¹

Plugging these value in equation (1) as :

ln (\frac{1.0 ppm}{10.3 ppm} ) = - 0.0241 yrs^-^1 * t

ln (0.0971 ) = -0.0241 yrs ^-^1 * t

(ln 0.0971 = - 2.33 )

Dividing both side by - 0.0241 yrs⁻¹

\frac{-2.33}{-0.0241 yrs^-^1} = \frac{-0.0241 yrs^-^1 * t}{-0.0241 yrs^-^1}

t = 96.68 yrs

Hence the concentration of Strontium-90 will drop from 10.3 ppm to 1.0 ppm is 96.68 yrs

3 0
3 years ago
Read 2 more answers
Select True or False from the pull down menus for the following statements.
Shkiper50 [21]

Answer:

First question: 1- False, 2- True, 3- False, 4 -Tue, 5- True.

Second question: 12.7 ºC

Explanation:

First question:

1- When a phase change for a pure substance is taking place under constant pressure, the temperature remains constant, and there's no sensitive heat flowing, but there's latent heat flow, which must be added to separate the molecules and to increase the kinetic energy.

2- When observed the heating and the cooling curve, at the phase change, there is no change in temperature, so it must be a horizontal line, which has a slope equal to 0.

3- Heat is the energy that is transferred by the substances or bodies because of a difference in temperature. The temperature is the measure of average kinetic energy in the molecules, so they are different.

4- As explained above, it's true, that's the definition of temperature.

5- Melting and freezing are the opposite processes and they occur at the same temperature. The difference is that for melting, the substance is absorbing heat, and for freezing it is losing heat, but the heat amount is the same for both process and is calculated by Q = ±m*L, where Q is the heat, m the mass, L the heat capacity, and the signal ± indicates if the substance is absorbing (+) or losing (-) heat.

Second question:

For the conservation of energy, the total amount of heat must be 0. The coin is losing heat, so it must be negative. The water is gaining heat, so it must be positive:

Qw - Qc = 0

Q = m*s*ΔT, where Q is the heat, m is the mass, s is the specif heat, and ΔT the temperature variation (final - initial). Qw is from water and Qc for the coin. The specif heat from the water is 4.184 J/gºC. At the thermal equilibrium, the final temperature must be equal for both.

mw*sw*ΔTw = mc*sc*ΔTc, if the coin is pure silver, sc = 0.233 J/gºC

27.0*4.184*(T - 15.5) = 15.5*0.233*(T - 100)

112.968*(T - 15.5) = 3.6115*(T - 100)

112.968T - 1751.004 = 3.6115T - 361.15

109.3565T = 1389.854

T = 1389.854/109.3565

T = 12.7ºC

So, the final water temperature would be 12.7ºC, which is impossible because it needs to increase. So the coin is not silver pure.

7 0
3 years ago
could you please explain operations with scientific notation using this example. 5 × 10³ + 4.3 × 10⁴ i dont understand how to so
TEA [102]

Explanation:

The scientific notation:

a\times10^k

where

1\leq a and k is integer.

We have the example:

(5\times10^3)+(4.3\times10^4)

You can write the numbers in a "normal" form:

5\times10^3=5\times1000=5000\\\\4.3\times10^4=4.3\times10000=43000

Make the sum:

5000+43000=48000

And next write it in the scientific notation:

48000=4\underbrace{8000}_{\leftarrow4}=4.8000\times10000=4.8\times10^4

<h3>Other method:</h3>

You can add numbers in scientific notation if the power of tens in both number is the same.

Therefore you must convert the first number:

5\times10^3=0.5\times10\times10^3=0.5\times10^4

Now, you can make the sum:

(5\times10^3)+(4.3\times10^4)=0.5\times10^4+4.3\times10^4=(0.5+4.3)\times10^4=4.8\times10^4

4 0
2 years ago
For every 4 hours that Alexa babysit her younger sister, her mom pays her $50
tiny-mole [99]

Answer:12.5

Explanation: Divide 50$ by the 4 hours and you will get 12.5 which is $12.50.

7 0
3 years ago
Read 2 more answers
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