What is 0.00000005 in scientific notation, rounded to two significant figures?

When the sun shines directly on objects, white objects remain cooler than black objects. This difference in temperature is becau

Dimas [21]

Answer:

The amount of sun that is being reflected and how hot the sunlight being reflected is

Explanation:

6 0

3 years ago

If Iron (Fe) gained a proton what would it be?

Mkey [24]

If iron (Fe) gained a proton it would become cobalt (CO).

8 0

3 years ago

Write the rate law for the reaction 2A + B → C if the reaction

konstantin123 [22]

Answer:

1. $R=k[A]^1[B]^2$

2. $R=k[B]^1$

3. $R=k[A]^0[B]^0=k$

4. $R=k[A]^1[B]^{-1}$

Explanation:

Rate law says that rate of a reaction is directly proportional to the concentration of the reactants each raised to a stoichiometric coefficient determined experimentally called as order.

(1) is second order in B and overall third order.

2A + B → C

Order of the reaction = sum of stoichiometric coefficient

= x + 2 = 3

x = 1

Rate of the reaction =R

$R=k[A]^1[B]^2$

(2) is zero order in A and first order in B.

2A + B → C

Rate of the reaction =R

$R=k[A]^0[B]^1=k[B]^1$

Order of the reaction = sum of stoichiometric coefficient

= 0 + 1 = 1

(3) is zero order in both A and B .

2A + B → C

Order of the reaction = sum of stoichiometric coefficient

= 0 + 0 = 0

Rate of the reaction =R

$R=k[A]^0[B]^0=k$

(4) is first order in A and overall zero order.

2A + B → C

Order of the reaction = sum of stoichiometric coefficient

= 1 + x = 0

x = -1

Rate of the reaction = R

$R=k[A]^1[B]^{-1}$

4 0

3 years ago

Please check if i did it right. did i put the right electric charge

Ad libitum [116K]

Your protons are correct but it’s 28 neutrons not 27!

6 0

3 years ago

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

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