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4 years ago

Why do metals change in appearance over time?

1 answer:

5 0

The exterior surface of metal can be changed by many chemical reaction takes place the reaction is carried out by presence of oxygen and water in air which Demage shiny surface of metal. The other processes can also be involved as pollution, moisture and environmental change can also effect on the surface of metal.

If metal is keept in open environment for a long time moisture contents in air boats the corrosion and rusting of metal processes.

Hopefully you will understand.

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1. A gas having the following composition is burnt under a boiler with 50% excess air.

jeka94

The composition of the stack gas are :

$CH_4$ = 0.8713

$C_3H_8$ = 0.0202

CO = 0.107

<h3 /><h3>What is a mole fraction?</h3>

The ratio of the number of moles of one component of a solution or other mixture to the total number of moles representing all of the components.

Assuming 100 g of the stack gas. Calculate the mass of each species in this sample according to their percentages.

Mass of $CH_4$ : 70% of 100 g = 70 g

Mass of $C_3H_8$ : 15% of 100 g = 15 g

Mass of CO : 15% of 100 g = 15 g

Now calculate the number of moles of each species:

Number of moles of $CH_4$ : $\frac{70 g}{16.04 g/mol}$ = 4.3 mole

Number of moles of $C_3H_8$ : $\frac{15 g}{144.1 g/mol}$ = 0.10 mole

Mass of CO : $\frac{15 g}{28.01 g/mol}$ = 0.53 mole

Now to calculate the mole fraction of each we use the formula:

Mole fraction of $CH_4$ : $\frac{4.3}{4.935}$ = 0.8713

Mole fraction of $C_3H_8$ : $\frac{0.10}{4.935}$ = 0.0202

Mole fraction of CO : $\frac{0.53}{4.935}$ = 0.107

Hence, composition of the stack gas are:

$CH_4$ = 0.8713

$C_3H_8$ = 0.0202

CO = 0.107

Learn more about mole fraction here:

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8 0

3 years ago

Why is cellular reparation important for cells?

sladkih [1.3K]

Respiration aids in replenishing O2 and decrease the CO2 level in the cell. O2 is an important receiver in the oxidative respiration chain in the mitochondria, which is responsible for producing ATP for the cell. ATP can be considered as the “energy currency” of the cell. Many biochemical reactions in the cell requires ATP, including the operations of ion channels, buffer systems, transportation via vesicles, etc. Therefore if there is no O2, the cell cannot produce ATP and will die.

4 0

3 years ago

All methods of chromatography operate on the same basic principle that Select one: a. one component of the mixture will chemical

ANEK [815]

Answer:C

Explanation:

Chromatography separates compounds by taking advantage of their polarity. The stationary phase is generally very polar. The mobile phase can be pure hexane or various ratios of hexane with a polar eluent added. The more polar the compound, the more it interacts with the stationary phase and won’t move very far up the plate compared to the non-polar or less polar compounds that interact more with the non-polar hexane.

8 0

3 years ago

Bohr models notes The number of periods shows you the number of _______

lorasvet [3.4K]

Answer:

The number of periods shows you the number of _______

Electron Shell

Explanation:

Modern periodic table is divided into Groups and Periods.

A period is the horizontal row of the periodic table. There are seven periods in the periodic table.

It describes the following :

The period in which a particular element found will show its electron shell

The first period has Hydrogen and Helium = 1 - shell

The second Period has Lithium to neon = 2- shells

A group is the vertical column of the periodic table . There are 18 groups in total.

It describes the following :

The group number of the element is same as the number of electrons in the outermost shell.

The element having group 1 has = 1 electron in outer shell (example Na, K)

The element having group 2 has = 2 electron in outer shell (example Ca, Mg)

The element having group 0 has = full outer shell (example Ne Xe). these are also known as noble gases

8 0

4 years ago

What does the model represent

Alona [7]

The model represents Photosynthesis. Light, carbon dioxide, and water are the reactants. The products will be Sugar and Oxygen. Photosynthesis releases oxygen and glucose. Which is the energy that living things need to survive.

6 0

3 years ago