Which statement is true of the hydrogenation of benzene?

Thermodynamic PropertiesProperty Value

igomit [66]

Answer:

1,620 J.

Explanation:

The amount of heat added to a substance (Q) can be calculated from the relation:

Q = m.c.ΔT.

where, Q is the amount of heat released from ethanol cooling,

m is the mass of ethanol (m = 60.0 g),

c is the specific heat of ethanol in the liquid phase, since the T is cooled below the boiling point and above the melting point (c = 1.0 J/g °C),

ΔT is the temperature difference (final T - initial T) (ΔT = 43.0 °C – 70.0 °C = - 27.0 °C).

∴ Q = m.c.ΔT = (60.0 g)(1.0 J/g °C)(- 27.0 °C) = - 1620 J.

The system releases 1620 J.

8 0

3 years ago

Why is it so difficult

Sergeeva-Olga [200]

Because teachers don’t really understand it all that well themselves so they can’t teach it effectively

5 0

2 years ago

Read 2 more answers

What does the 2 mean in the formula 5Mg3(PO4)2? There are two elements in magnesium phosphate. There are two molecules of magnes

frozen [14]

Answer: In this compound, phosphorous and oxygen act together as one charged particle, which is connected to magnesium, the other charged particle.

Explanation:

4 0

3 years ago

PLEASE HELP! Find out whether the chemical equation is balanced or unbalanced.

nordsb [41]

One chemical reaction is called the Haber process, a method for preparing ammonia by reacting nitrogen gas with hydrogen gas:

This equation shows you what happens in the reaction, but it doesn’t show you how much of each element you need to produce the ammonia. To find out how much of each element you need, you have to balance the equation — make sure that the number of atoms on the left side of the equation equals the number of atoms on the right.

You know the reactants and the product for this reaction, and you can’t change them. You can’t change the compounds, and you can’t change the subscripts, because that would change the compounds.

So the only thing you can do to balance the equation is add coefficients, whole numbers in front of the compounds or elements in the equation. Coefficients tell you how many atoms or molecules you have.

For example, if you write the following, it means you have two water molecules:

Each water molecule is composed of two hydrogen atoms and one oxygen atom. So with two water molecules (represented above), you have a total of 4 hydrogen atoms and 2 oxygen atoms.

You can balance equations by using a method called balancing by inspection. You take each atom in turn and balance it by adding appropriate coefficients to one side or the other.

With that in mind, take another look at the equation for preparing ammonia: HOPE THIS HELPS

4 0

3 years ago

. The heat capacity of a bomb calorimeter was determined by burning 6.79 g methane (energy of combustion 802 kJ/mol CH4) in the

kolbaska11 [484]

Answer:

a) The heat capacity of the calorimeter is 31.4 kJ/ºC.

b) The energy of combustion of acetylene in kJ/mol is 1097 kJ/mol.

Explanation:

The heat capacity ( C ) of a substance is the amount of heat required to raise the temperature of a given quantity of the substance by one degree Celsius. Its units are J/°C. or kJ/ºC.

If we know the heat capacity and the amount of a substance, then the change in the sample’s temperature (Δt ) will tell us the amount of heat (q) that has been absorbed or released in a particular process. One of the equations for calculating the heat change is given by:

$q=C.ΔT$

Where ΔT is the temperature change: ΔT= tfinal - tinitial, and C the heat capacity.

In the calorimeter, the heat given off by the sample is absorbed by the water and the bomb. The special design of the calorimeter enables us to assume that no heat (or mass) is lost to the surroundings during the time it takes to make measurements.

Therefore, we can call the bomb and the water in which it is submerged an isolated system. Because no heat enters or leaves the system throughout the process, the heat change of the system ( q system ) must be zero and we can write:

$qsystem = qrxn + qcal$

$qsystem = 0$

where q cal and q rxn are the heat changes for the calorimeter and the reaction, respectively. Thus, $qrxn = -qcal$

To calculate qcal , we need to know the heat capacity of the calorimeter ( Ccal ) and the temperature rise, that is, $qcal = Ccal. ΔT$

a. The quantity Ccal is calibrated by burning a substance with an accurately known heat of combustion. In order to do this, we need to convert the molar heat of combustion (expressed in kJ/mol) into heat of combustion (expressed in kJ). For that matter, we transform the 6.79 grams of methane into moles:

$1 mol CH₄÷16.04 g CH₄ × 6.79 g CH₄ = 0.423 mol CH₄$

And then multiply it by the molar heat of combustion:

$802 kJ/mol × 0.423 mol = 339 kJ$

Now we know that that the combustion of 6.79 g of methane releases 339 kJ of heat. If the temperature rise is 10.8ºC, then the heat capacity of the calorimeter is given by

$Ccal= qcal/ΔT = 339 kJ/10.8ºC = 31.4 kJ/ºC$

Once C cal has been determined, the calorimeter can be used to measure the heat of combustion of other substances. Note that although the combustion reaction is exothermic, q cal is a positive quantity because it represents the heat absorbed by the calorimeter.

b. The heat absorbed by the bomb and water is equal to the product of the heat capacity and the temperature change. Working with the same equation, and assuming no heat is lost to the surroundings, we write

$qcal=Ccal.ΔT= 31.4 kJ/°C × 16.9 °C = 531kJ$

Now that we have the heat of combustion, we need to calculate the molar heat. Because qsystem = qrxn + qcal and qrxn = -qcal, the heat change of the reaction is -531 kJ.

This is the heat released by the combustion of 12.6 g of acetylene ; therefore, we can write the conversion factor as 531 kJ÷12.6 g

The molar mass of acetylene is 26.04 g, so the heat of combustion of 1 mole of acetylene is

$molar heat of combustion= -531 kJ÷12.6 g × 26.04 g÷ 1 mol= 1097 kJ/mol$

Therefore, the energy of combustion of acetylene in kJ/mol is 1097 kJ/mol.

7 0

4 years ago