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tankabanditka [31]
2 years ago
8

Can someone help me with this question pls?

Chemistry
1 answer:
vlada-n [284]2 years ago
7 0

Explanation:

frequency = 1 wave/10s = 0.1 Hz

wavelength = 5.8 m

speed = wavelength × frequency

= (5.8 m)(0.1 Hz)

= 0.58 m/s

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i am begging anyone to help me with this! (all tutors i've asked said they can't solve it but i need someone to help me out) - i
9966 [12]

First, we need to calculate how much energy we will get from this combustion.

Assuming the combustion is complete, we have the octane reacting with O₂ to form only water and CO₂, so:

C_8H_{18}+O_2\to CO_2+H_2O

We need to balance the reaction. Carbon only appear on two parts, so, we can start by it:

C_8H_{18}+O_2\to8CO_2+H_2O

Now, we balance the hydrogen:

C_8H_{18}+O_2\to8CO_2+9H_2O

And in the end, the oxygen:

C_8H_{18}+\frac{25}{2}O_2\to8CO_2+9H_2O

We can multiply all coefficients by 2 to get integer ones:

2C_8H_{18}+25O_2\to16CO_2+18H_2O

Now, we need to use the enthalpies of formation to get the enthalpy of reaction of this reaction.

The enthalpy of reaction can be calculated by adding the enthalpies of formation of the products multiplied by their stoichiometric coefficients and substracting the sum of enthalpies of formation of the reactants multiplied by their stoichiometric coefficients.

For the reactants, we have (the enthalpy of formation of pure compounds is zero, which is the case for O₂):

\begin{gathered} \Delta H\mleft\lbrace reactants\mright\rbrace=2\cdot\Delta H\mleft\lbrace C_8H_{18}\mright\rbrace+25\cdot\Delta H\mleft\lbrace O_2\mright\rbrace \\ \Delta H\lbrace reactants\rbrace=2\cdot(-250.1kJ)+25\cdot0kJ \\ \Delta H\lbrace reactants\rbrace=-500.2kJ+0kJ \\ \Delta H\lbrace reactants\rbrace=-500.2kJ \end{gathered}

For the products, we have:

\begin{gathered} \Delta H_{}\mleft\lbrace product\mright\rbrace=16\cdot\Delta H\lbrace CO_2\rbrace+18\cdot\Delta H\lbrace H_2O\rbrace \\ \Delta H_{}\lbrace product\rbrace=16\cdot(-393.5kJ)+18\cdot(-285.5kJ) \\ \Delta H_{}\lbrace product\rbrace=-6296kJ-5139kJ \\ \Delta H_{}\lbrace product\rbrace=-11435kJ \end{gathered}

Now, we substract the rectants from the produtcs:

\begin{gathered} \Delta H_r=\Delta H_{}\lbrace product\rbrace-\Delta H\lbrace reactants\rbrace \\ \Delta H_r=-11435kJ-(-500.2kJ) \\ \Delta H_r=-10934.8kJ \end{gathered}

Now, this enthalpy of reaction is for 2 moles of C₈H₁₈, so for 1 mol of C₈H₁₈ we have half this value:

\Delta H_c=\frac{1}{2}\Delta H_r=\frac{1}{2}\cdot(-10934.8kJ)=-5467.4kJ

Now, we have 100 g of C₈H₁₈, and its molar weight is approximately 114.22852 g/mol, so the number of moles in 100 g of C₈H₁₈ is:

\begin{gathered} M_{C_8H_{18}}=\frac{m_{C_8H_{18}}}{n_{C_8H_{18}}} \\ n_{C_8H_{18}}=\frac{m_{C_8H_{18}}}{M_{C_8H_{18}}}=\frac{100g}{114.22852g/mol}\approx0.875438mol \end{gathered}

Since we have approximately 0.875438 mol, and 1 mol releases -5467.4kJ when combusted, we have:

Q=-5467.4kJ/mol\cdot0.875438mol\approx-4786.37kJ

Now, for the other part, we need to calculate how much heat it is necessary to melt a mass, <em>m</em>.

First, we have to heat the ice to 0 °C, so:

\begin{gathered} Q_1=m\cdot2.010J/g.\degree C\cdot(0-(-10))\degree C \\ Q_1=m\cdot2.010J/g\cdot10 \\ Q_1=m\cdot20.10J/g \end{gathered}

Then, we need to melt all this mass, so we use the latent heat now:

Q_2=n\cdot6.03kJ/mol

Converting mass to number of moles of water we have:

\begin{gathered} M=\frac{m}{n} \\ n=\frac{m}{M}=\frac{m}{18.01528g/mol} \end{gathered}

So:

Q_2=\frac{m}{18.01528g/mol}_{}\cdot6.03kJ/mol\approx m\cdot0.334716kJ/g

Adding them, we have a total heat of:

\begin{gathered} Q_T=m\cdot20.10J/g+m\cdot0.334716kJ/g \\ Q_T=m\cdot0.02010kJ/g+m\cdot0.334716kJ/g \\ Q_T=m\cdot0.354816kJ/g \end{gathered}

Since we have a heat of 4786.37 kJ form the combustion, we input that to get the mass (the negative sign is removed because it only means that the heat is released from the reaction, but now it is absorbed by the ice):

\begin{gathered} 4786.37kJ=m\cdot0.354816kJ/g \\ m=\frac{4786.37kJ}{0.354816kJ/g}\approx13489g\approx13.5\operatorname{kg} \end{gathered}

Since we have a total of 20kg of ice, we can clculate the percent using it:

P=\frac{13.5\operatorname{kg}}{20\operatorname{kg}}=0.675=67.5\%

5 0
1 year ago
Suppose water did not form hydrogen bonds.
Vilka [71]

-70°C

Sink

little

hydrogen bonding

Explanation:

Completing the statements:

Water's boiling point would have been close to -70°C. Ice would sink in water. Water would release little heat to warm land during the winter. Ice is less dense than water because of the hydrogen bonding that forms a hexagonal structure in water.

The unique property of water is as a result of its hydrogen bonding. Water is a polar covalent compound. Like most covalent compound, water would have naturally had a very low boiling point.

The intermolecular forces all hydrogen bonding gives water its unique nature.

Hydrogen bond is formed by an attraction between hydrogen one water water molecule and  more electronegative atom on another molecule usually oxygen, nitrogen and fluorine.

They form very strong intermolecular interaction responsible for the behavior of water.

The higher specific heat capacity of water is due to this bond. It absorbs a lot of heat and does not release them on time. This causes water release heat during winter.

Water has a hexagonal shape or structure linking each molecules.

learn more;

Hydrogen bonding brainly.com/question/10602513

#learnwithBrainly

5 0
3 years ago
Read 2 more answers
How many atoms of potassium and how
Varvara68 [4.7K]
KOH? 6.022 x 10^23 atoms of potassium(K) are in one mole of KOH
8 0
3 years ago
Enter your answer in the provided box.A mixture of helium and neon gases is collected over water at 28°C and 791 mmHg. If the pa
polet [3.4K]

Answer:

Explanation:

Using Dalton's law of partial pressure

P total pressure = Pressure of helium + Pressure of neon + Vapor pressure of water

P = 28.3 mmHg, Pressure of helium = 381 mmHg, Vapor pressure of water at 28°C

791 mmHg - 381 mmHg - 28.3 mmHg = Pressure of neon

Pressure of neon = 381.7 mmHg

7 0
3 years ago
Choose the correct answer.
marishachu [46]

Answer:

B. Of

Explanation:

They had good taste of music.

But I think 'in' is the best preposition.

4 0
3 years ago
Read 2 more answers
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