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2 years ago

Which statement explains why catalysts are important for living

Chemistry

1 answer:

Marina86 [1]2 years ago

8 0

Answer:

Catalysts allow chemical reactions to occur at temperatures at which the organism lives.

Explanation:

Catalysts are molecules that speeden the rate of chemical reaction by lowering the activation energy of the reaction. In a living system, the catalyst are ENZYMES, which help to hasten up many biochemical reactions.

Another function of catalyst in living systems is that it allows chemical reactions to occur at temperatures at which the organism lives.

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The unit cell for cr2o3 has hexagonal symmetry with lattice parameters a = 0.4961 nm and c = 1.360 nm. If the density of this ma

IRINA_888 [86]

To calculate the packing factor, first calculate the area and volume of unit cell.

Area is calculated as:

$A=6R^{2}\sqrt{3}$

Here, R is radius and is related to a as follows:

$R=\frac{a}{2}$

Putting the value in expression for area,

$A=6(\frac{a}{2})^{2}\sqrt{3}=1.5a^{2}\sqrt{3}$

The value of a is 0.4961 nm

Since, $1 nm=10^{-7}cm$

Thus, $0.4961 nm=4.961\times 10^{-8} cm$

Putting the value,

$Area=1.5(4.961\times 10^{-8}cm)^{2}\sqrt{3}=6.39\times 10^{-15}cm^{2}$

Now, volume can be calculated as follows:

$V=Area\times c$

The value of c is 1.360 nm or $1.360\times 10^{-7} cm$

Putting the value,

$V=(6.39\times 10^{-15}cm^{2})\times (1.360\times 10^{-7} cm)=8.7\times 10^{-22}cm^{3}$

now, number of atom in unit cell can be calculated by using the following formula:

$n=\frac{\rho N_{A}V_{c}}{A}$

Here, A is atomic mass of $Cr_{2}O_{3}$ is 151.99 g/mol.

Putting all the values,

$n=\frac{(5.22 g/cm^{3})(6.023\times 10^{23} mol^{-1})(8.7\times 10^{-22}cm^{3})}{(151.99 g/mol)}\approx 18$

Thus, there will be 18 $Cr_{2}O_{3}$ units in 1 unit cell.

Since, there are 2 Cr atoms and 3 oxygen atoms thus, units of chromium and oxygen will be 2×18=36 and 3×18=54 respectively.

The atomic radii of $Cr^{3+}$ and $O^{2-}$ is 62 pm and 140 pm respectively.

Converting them into cm:

$1 pm=10^{-10}cm$

Thus,

$r_{Cr^{3+}}=6.2\times 10^{-9}cm$

and,

$r_{O^{2-}}=1.4\times 10^{-8}cm$

Volume of sphere will be sum of volume of total number of cations and anions thus,

$V_{S}=V_{Cr^{3+}}+V_{O^{2-}}$

Since, volume of sphere is $V=\frac{4}{3}\pi r^{3}$ ,

$V_{S}=36\left ( \frac{4}{3}\pi (r_{Cr^{3+})^{3}} \right )+54\left ( \frac{4}{3}\pi (r_{O^{2-})^{3}} \right )$

Putting the values,

$V_{S}=36\left ( \frac{4}{3}(3.14) (6.2\times 10^{-9} cm)^{3}} \right )+54\left ( \frac{4}{3}(3.14) (1.4\times 10^{-8} cm)^{3}} \right )=6.6\times 10^{-22}\times 10^{-8}cm^{3}$

The atomic packing factor is ratio of volume of sphere and volume of crystal, thus,

$packing factor=\frac{V_{S}}{V_{C}}=\frac{6.6\times 10^{-22}cm^{3}}{8.7\times 10^{-22}cm^{3}}=0.758$

Thus, atomic packing factor is 0.758.

6 0

3 years ago

Read 2 more answers

Three other application of Bernoulli's principle ?

Makovka662 [10]

<h2><u>Answer:</u></h2>

Bernoulli's Theorem in a general sense relates the weight, speed, and rise in a moving fluid (liquid or gas), the compressibility and consistency (internal grinding) of which are insignificant and the flood of which is predictable, or laminar.

(1): We can discover the speed of Efflux of a fluid.

This is given by v= sqrt (2gh), where the fluid is turning out from an opening in a vessel at profundity h from free fluid surface. This condition is known as Torricelli's hypothesis.

(2): Vena Contracta: The fluid stream from gap contracts at a separation minimal outside the opening to a neck, called Vena Contracta.

The territory of cross-segment of a fly is littler than a zone of opening. From this reality, we can discover the coefficient of withdrawal.

(3) : Bernoulli's standard is utilized in the development of Venturimeter, an instrument for estimation of measure of a stream of a fluid through a pipe.

7 0

3 years ago

Hello! I just need a little bit of help. I'm supposed to design an experiment on how reaction rates are determined and affected

alexandr1967 [171]

Get 3 cups of water at the exact same temperature, using the thermometer to check.
Label the cups as ‘whole’, ‘pieces’, and ‘crushed’
Next, get something to dissolve, in this case, polident. Take one of the polident tablets and break it into 4 pieces, and set it aside.
Take another polident tablet and this time put it into a different cup, and crush it. Set it aside.
Keep the last tablet whole.
Set up your stopwatch and drop the polident tablet that is whole in the cup labeled ‘whole’, starting the stopwatch at the same time.
Watch the cup and see when the tablet is fully dissolved, then stop the stopwatch.
Record the time in the table.
Repeat steps 6-8 for both the ‘pieces’ and ‘crushed’ tablets.

Hope this helps! Please let me know if you need more help, or if you think my answer is incorrect. Brainliest would be MUCH appreciated. Have a great day!

Stay Brainy!

− $xXheyoXx$

3 0

2 years ago

Write the formula and calculate the molecular mass of

Reika [66]

The molecular formula is the sum of the atomic masses of all atoms in the molecule.

The formula of Soda Ash:

Na₂CO₃ is also known as Sodium Carbonate.

The molecular mass of Soda Ash is

(2×Na)+(1×C)+(3×O)=106g/mol

The formula of Baking Soda:

NaHCO₃ is also known as Sodium bicarbonate.

The molecular mass of Baking Soda is

(1×Na)+(1×H)+(1×C)+(3×O)=84g/mol

The formula of Lime Stone:

CaCO₃ is also known as Calcium carbonate.

The molecular mass of Lime Stone:

(1×Ca)+(1×H)+(1×C)+(3×O)=100g/mol

The formula of Ethanol:

C₂H₅OH is the formula of ethanol.

The molecular mass of Ethanol:

(2×C)+(6×H)+(1×O)=46g/mol

The formula of Common Salt:

NaCl is also known as Sodium chloride.

The molecular mass of Common Salt:

(1×Na)+(1×Cl)=58.5g/mol

Learn more about chemical formulas here:

brainly.com/question/26694427

#SPJ10

7 0

2 years ago

Whats the correct order of these?

Igoryamba

1109, 5.9 * 10 squared, -0.041, -4.2 times 10 to the -3, and -7.6 times 10 to the -5
Hope this helps

3 0

3 years ago