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3 years ago

How do you work out question 1a?

Chemistry

1 answer:

Sliva [168]3 years ago

4 0

Answer:

-125 kJ

Explanation:

You calculate the energy required to break all the bonds in the reactants. Then you subtract the energy to break all the bonds in the products.

H₂C=CH₂ + H₂ ⟶ H₃C-CH₃

Bonds: 4C-H + 1C=C 1H-H 6C-H + 1C-C

D/kJ·mol⁻¹: 413 612 436 413 347

The formula relating ΔHrxn and bond dissociation energies (D) is

ΔHrxn = Σ(Dreactants) – Σ(Dproducts)

(Note: This is an exception to the rule. All other thermochemical reactions are “products – reactants”. With bond energies, it’s “reactants – products”. The reason comes from the way we define bond energies.)

For the reactants:

Σ(Dreactants) = 4 × 413 + 1 × 612 + 1 × 436 = 2700 kJ

For the products:

Σ(Dproducts) = 6 × 413 + 1 × 347 = 2825 kJ

For the system :

ΔHrxn = 2700 - 2825 = -125 kJ

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Define natural gas, liquefied petroleum gas (LPG), and liquefied natural gas (LNG). What three countries have most of the world’

mrs_skeptik [129]

Answer:

The answer is treated below.

Explanation:

Natural gas: Natural gas is not used in its pure form; it is processed and converted into cleaner fuel for consumption. It is a fossil fuel composed almost entirely of methane, but contain small amounts of other gases, including ethane, propane, pentane and butane. It is a combustible, gaseous mixture of simple hydrocarbon compounds, usually found in deep underground reservoirs formed by porous rock. Natural gas is mainly used as fuel for generating heat and electricity.

Liquefied petroleum gas (LPG): Liquefied Petroleum Gas is a byproduct of natural gas and oil extraction and crude oil refining . At room temperature, liquefied petroleum gas is a colourless and odourless gas which consists generally of butane (C4H10) or propane (C3H8) or a mixture of both.

Liquefied natural gas (LNG): Is natural gas that has been liquefied for ease of transport or storage. It is refrigerated to a very low temperature (-162 Celsius). At this temperature it becomes an odourless, non-toxic liquid that can be safely transported over long distances.

Three countries that have most of the world’s natural gas reserves

Russia
Iran
Qatar

Major advantages of using conventional natural gas as an energy resource:

It is less expensive when compared to other fossil fuels.
It is safer and easier to store when compared to other fossil fuels

Major disadvantages of using conventional natural gas as an energy resource:

It costs more to recover the remaining natural gas because of flow, access, etc.
It is not a renewable source.
it is a combustible material, It must be handled with care.
It does not contribute to greenhouse gases.

Three sources of unconventional natural gas :

Tight Gas
Shale Gas
Coalbed Methane

Major problems related to the use of Tight Gas

When Hydrofluoric acid is used to release tight gas in reserves it potentially an issue simply because the substance is so dangerous. A spill or a leak could harm workers and pollute groundwater for uses.

Major problems related to the use of Shale Gas

Risk of ground and surface water contamination.
Have impacts on air quality.

Major problems related to the use of Coalbed Methane

The development of coalbed methane will result to soil disturbance from construction of wells, roads, and the associated pipeline and electric power rights-of-ways.
It has impact on wildlife.

8 0

3 years ago

An animal cell has a 0.9% saline environment is placed into a solution that is 9% saline. What will happen to the cell

Softa [21]

The concentration of cell is less than that of the solution .

Hence the cell will be called as hypotonic and the solution will be called as hypertonic.

in order to balance the concentration on the two sides of cell (inside and outside in the solution) there will be movement of solvent particles (through semipermeable membrane ) from cell (lower concentration of solute) to solution (higher concentration of solute).

Thus cell will shrink.

7 0

3 years ago

An aqueous solution of sodium

DochEvi [55]

Answer:

2.5×10^-7mol/dm^3

Explanation:

Firstly convert the cm^3 to dm^3

200×1000=200000dm^3

Calculate the g/dm^3

2/200000=0.00001g/dm^3

To calculate mol/dm^3

Mol/dm^3=mass given\molar mass

=0.00001/40

=2.5×10^-7mol/dm^3

8 0

3 years ago

Read 2 more answers

What new evidence led scientists to change their minds about the geocentric model?

IRISSAK [1]

Galileo disproved the Ptolemaic theory, sanctioned for centuries by the Church, which held the Earth to be the central and principal object in the universe, about which all celestial objects orbited.

3 0

3 years ago

The atomic masses of 151eu and 153eu are 150.919860 and 152.921243 amu, respectively. The average atomic mass of europium is 151

vitfil [10]

Answer:- The natural abundance of $^1^5^1_E_u$ is 0.478 or 47.8% and $^1^5^3_E_u$ is 0.522 or 52.2% .

Solution:- Average atomic mass of an element is calculated from the atomic masses of it's isotopes and their abundances using the formula:

Average atomic mass = mass of first isotope(abundance) + mass of second isotope(abundance)

We have been given with atomic masses for $^1^5^1_E_u$ and $^1^5^3_E_u$ as 150.919860 and 152.921243 amu, respectively. Average atomic mass of Eu is 151.964 amu.

Sum of natural abundances of isotopes of an element is always 1. If we assume the abundance of $^1^5^1_E_u$ as n then the abundance of $^1^5^3_E_u$ would be 1-n .

Let's plug in the values in the formula:

$151.964=150.919860(n)+152.921243(1-n)$