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3 years ago

Estimate the heat released when ethene (CH2=CH2) reacts with HBr to give CH3CH2Br.

Chemistry

1 answer:

bonufazy [111]3 years ago

7 0

Answer:

Explanation:

The reaction between ethene and HBr is:

CH2=CH2 + HBr → CH3CH2Br

Thus, the double bond C=C and the bond H-Br were broken, and the bonds C-C, C-H and C-Br were formed. The enthalpy of the reaction (the energy change), is the sum of the enthalpies of the reactions that were broken with the bonds that were created.

To break a bond, it's necessary to the molecule to gain energy, thus the process is endothermic and H>0, and to form a bond, it's necessary to release energy, and so H<0, so:

ΔH = ∑n*Hbroken - ∑n*Hformed, where n is the coefficient of the substance, so:

ΔH = (612 + 366) - (348+412+276)

ΔH = -58 kJ/mol

The minus signal indicates that the energy was released.

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4 years ago

How many joules of energy do you have if you have 0.45 L of water in a can and you heat the 23C water to 55C site:socratic.org

Bess [88]

Answer:

Q = 60192 j

Explanation:

Given data:

Volume of water = 0.45 L

Initial temperature = 23°C

Final temperature = 55°C

Amount of heat absorbed = ?

Solution:

Formula:

Q = m.c. ΔT

Q = amount of heat absorbed or released

m = mass of given substance

c = specific heat capacity of substance

ΔT = change in temperature

ΔT = 55°C - 23°C

ΔT = 32°C

one L = 1000 g

0.45 × 1000 = 450 g

Specific heat capacity of water is 4.18 j/g°C

Q = m.c. ΔT

Q = 450 g. 4.18 j/g°C. 32°C

Q = 60192 j

4 0

3 years ago

Elements occur in a number of isotopic forms. In this problem, you will learn about the notation used to distinguish different i

alina1380 [7]

Answer:

Number of protons, Z = 14
Number of neutrons, N = 14

Explanation:

1) About isotopes:

Isotopes are different kind of atoms of the same element. Hence, they have the atomic number (Z), which is the number of protons, the same number of electrons (talking about to neutral atoms, not ions), and different number of neutrons N).

This is, it is the number of neutrons what distinguish different isotopes of an element.

2) About the notation used to distinguish different isotopes:

A superscript and a subscript, both to the left of the chemical symbol of the element, are used to distinguish different isotopes:

A ←------------- This superscript tells the mass number of the isotope

X ←--------- This is the chemical symbol of the element

Z ←-------------- This subscript is the atomic number of isotope

In our case, the notiation for the isotope of silicon is: ²⁸₁₄ Si

So, we have:

28 is the mass number (A)
14 is the atomic number (Z)
Si is the chemical symbol.

Now, you can answer the questions of the part A:

Number of protons: Z = 14

Number of neutrons N:

mass number = number of protons + number of neutrons

A = Z + N

⇒ N = A - Z = 28 - 14 = 14

In conclusion:

Number of protons, Z = 14
Number of neutrons, N = 14

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3 years ago