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3 years ago

Sacrificial protection takes place when a magnesium block is

Chemistry

1 answer:

Liula [17]3 years ago

6 0

Answer:

Explained below.

Explanation:

In oil rigs, Sacrificial protection is the protection of the steel against corrosion by using magnesium block which is a more reactive metal. This means that steel which is to be protected from corrosion will be the cathode while magnesium block preventing it from corrosion will be the anode and as such the block will be the one to corrode instead.

The mechanism behind this sacrificial protection is that the steel pipe on the rig will be connected to the magnesium block through copper wires and then the magnesium block will donate its electrons to the steel thereby preventing it from rusting. Thus is a reversible reaction and as such, after the steel Iron undergoes oxidization by receiving electrons from the magnesium block, it will be immediately be reduced to iron as depicted in the equation below.

Mg⇌Mg^(2+) + 2e-

Fe^(2+) + 2e-⇌Fe

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serious [3.7K]

C. Fewer. it is a summary

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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

I need help with this pleae

pantera1 [17]

Depositional landforms are the visible evidence of processes that have deposited sediments or rocks after they were transported by flowing ice or water, wind or gravity. Examples include beaches, deltas, glacial moraines, sand dunes and salt domes

3 0

3 years ago

Which element is classified as an alkali metal? Rb Sr Zr Cl

qwelly [4]

Hi there.

Alkali metals are known as the group 1 elements.

When we know this, we just have to look to group 1 of the periodic table.

Rb (Rubidium) is in group 1; it is classified as an alkali metal.

~

4 0

3 years ago

Read 2 more answers

The only way to determine the products of a reaction is to carry out the reaction. All chemical reactions can be classified as o

myrzilka [38]

Answer:

All the statements are correct but "all chemical reactions can be classified as one of the five general types".

Explanation:

Hello,

In this case, I assume you are looking for the wrong statement as long as the following ones are correct and matches with the foundations of chemical reactions:

- The only way to determine the products of a reaction is to carry out the reaction. This is clear, because after the chemical reaction is done, one identifies the products.

- Complete combustion has occurred when all the carbon in the product is in the form of carbon dioxide. This is clear due to a 100% conversion.

- A single reactant is the identifying characteristic of a decomposition reaction. All decomposition reactions have only one reactant which breaks into less complex species.

So the wrong statement is:

- All chemical reactions can be classified as one of five general types. This is wrong because there are four widely known chemical reactions: synthesis, decomposition, simple displacement and double displacement.

Best regards.

8 0

4 years ago