The sun is located at 1 astronomical unit from Earth. How far is the next closest star to Earth?

A sample of hexane (C6H14) has a mass of 0.580 g. The sample is burned in a bomb calorimeter that has a mass of 1.900 kg and a s

Talja [164]

<u>Answer:</u> The enthalpy of the reaction is -4134.3 kJ/mol

<u>Explanation:</u>

To calculate the heat absorbed by the calorimeter, we use the equation:

$q=mc\Delta T$

where,

q = heat absorbed

m = mass of calorimeter = 1.900 kg = 1900 g (Conversion factor: 1 kg = 1000 g)

c = heat capacity of calorimeter = 3.21 J/g.K

$\Delta T$ = change in temperature = 4.542 K

Putting values in above equation, we get:

$q=1900g\times 3.21J/g.K\times 4.542K=27701.66J=27.7kJ$

Heat released by the calorimeter will be equal to the heat absorbed by the reaction.

<u>Sign convention of heat:</u>

When heat is absorbed, the sign of heat is taken to be positive and when heat is released, the sign of heat is taken to be negative.

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of hexane = 0.580 g

Molar mass of hexane = 86.18 g/mol

Putting values in above equation, we get:

$\text{Moles of hexane}=\frac{0.580g}{86.18g/mol}=0.0067mol$

To calculate the enthalpy change of the reaction, we use the equation:

$\Delta H_{rxn}=\frac{q}{n}$

where,

q = amount of heat released = -27.7 kJ

n = number of moles of hexane= 0.0067 moles

$\Delta H_{rxn}$ = enthalpy change of the reaction

Putting values in above equation, we get:

$\Delta H_{rxn}=\frac{-27.7kJ}{0.0067mol}=-4134.3kJ/mol$

Hence, the enthalpy of the reaction is -4134.3 kJ/mol

5 0

3 years ago

Why do the planets move in fixed orbits around the Sun?

quester [9]

Answer: Gravity.

Explanation:

Newton realized that the reason the planets orbit the Sun is related to why objects fall to Earth when we drop them. The Sun's gravity pulls on the planets, just as Earth's gravity pulls down anything that is not held up by some other force and keeps you and me on the ground.

6 0

3 years ago

PLS HURRY 25 points

Arte-miy333 [17]

Answer:

its has to be AAAAAAAAAA

7 0

3 years ago

Read 2 more answers

Chloroacetic acid, ClCH2COOH, has a pKa of 2.87. What are [H3O+], pH, [ClCH2COO−], and [ClCH2COOH] in 1.55 M ClCH2COOH?

Mademuasel [1]

Answer:

See explanation below

Explanation:

first to all, this is an acid base reaction where the chloroacetic acid is being dissociated in water. Therefore, is an equilibrium reaction.

ClCH₂COOH has a pKa of 2.87 so, the Ka would be:

pKa = -logKa ---> Ka = antlog(-pka)

Ka = antlog(-2.87)

Ka = 1.35x10⁻³

Now that we know the Ka, we need to write the chemical reaction and then, an ICE chart:

ClCH₂COOH + H₂O <----------> ClCH₂COO⁻ + H₃O⁺ Ka = 1.35x10⁻³

i) 1.55 0 0

c) -x +x +x

e) 1.55-x x x

Writting now the equilibrium reaction:

Ka = [H₃O⁺] [ClCH₂COO⁻] / [ClCH₂COOH]

Replacing the values of the chart:

1.35x10⁻³ = x² / 1.55-x

1.35x10⁻³(1.55-x) = x²

2.0925x10⁻³ - 1.35x10⁻³x = x²

x² + 1.35x10⁻³x - 2.0925x10⁻³ = 0 --> a = 1; b = 1.35x10⁻³x; c = 2.0925x10⁻³

From here we use the general equation for solve x in a quadratic equation which is:

x = -b±√(b² - 4ac) / 2a

Replacing the values we have:

x = -1.35x10⁻³ ±√(1.35x10⁻³)² - 4*1*(-2.0925x10⁻³) / 2

x = -1.35x10⁻³ ±√(8.37x10⁻³) / 2

x = -1.35x10⁻³ ± 0.091 / 2

x1 = -1.35x10⁻³ + 0.091 / 2 = 0.045 M

x2 = -1.35x10⁻³ - 0.091 / 2 = -0.046 M

In this case, we will take the positive value of x, in this case, x1.

With this value, the equilibrium concentrations are the following:

[H₃O⁺] = [ClCH₂COO⁻] = 0.045 M

[ClCH₂COOH] = 1.55 - 0.045 = 1.505 M

Finally the pH:

pH = -log[H₃O⁺]

pH = -log(0.045)

pH = 1.35

4 0

3 years ago

Draw the organic product formed when the following compounds undergo a substitution reaction: (c) formic acid and 2-methyl-1-pro

Vesnalui [34]

The organic product formed when the formic acid and 2-methyl-1-propanol compounds undergo a substitution reaction is 2-methylpropyl Methanoate.

<h3>What is Substitution reaction? </h3>

Substitution reaction is a reaction in which one group substitute the functional group of another organic compound or it can also be defined as a reaction that involves the replacement of one atom or group of atoms of a compound with another atom or group of atom.

<h3>Types of Substitution reaction</h3>

Substitution Reactions are basically of two types:

nucleophilic reaction and electrophilic reactions. These two types of substitution reactions differ in the types of atom that is attached to its original molecule. In the nucleophilic reactions, the atom is electron-rich species, on the other hand, in the electrophilic reaction, the atom is an electron-deficient species.

When the formic acid and 2-methyl-1-propanol compounds undergo a substitution reaction, esterification take place. Therefore, the product formed is an ester.

Thus we found that the organic product formed when the formic acid and 2-methyl-1-propanol compounds undergo a substitution reaction is 2-methylpropyl Methanoate.

learn more about Substitution reaction:

brainly.com/question/10143438

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8 0

2 years ago