Which sample of argon contains a total of 3.01 x 10^23 molecules at STP?

Which of the following is true of the mass of an object?

shtirl [24]

Answer:

Its mass is measured on a scale.

It is measured on a balance.

Explanation:

The mass of an object can easily be determined using a balance or weighing scale.

Mass is the amount of matter contained in a substance. it is has the same value every where and will not vary by geography or location.

Weight is the force on body due to gravity. It is a function of mass and acceleration due to gravity.

Both mass and weight are different.

They can both be measured using a weight device.

6 0

3 years ago

Which choice best explains how herd behavior helps young musk oxen survive?

laiz [17]

Answer:

A

Explanation:

'herd behavior' helps understand the question for the answer

7 0

3 years ago

Read 2 more answers

Which arrow represents the change of state described

Mama L [17]

Answer:N

Explanation:

6 0

3 years ago

Given following electron configurations, 1s22s22p63s23p64s23d104p65s24d9 and 1s22s22p63s23p64s23d104p65s14d10.

marusya05 [52]

Explanations:- Part 1: We could count the total number of electrons by looking at the electron configurations. Both of these electrons configurations have 47 electrons. If we look at the periodic table then 47 is the atomic number of silver. So, the name of the element is silver and its represented as Ag.

Part 2: As per the rule, Completely filled and half filled orbitals are more stable. First electron configuration has 9 electrons in 4d and we know that d is more stable if it has 5 electrons(half filled) or it has 10 electrons(full filled).

For stability reasons, one of the electron from 5s goes to 4d and for this reason the second electron configuration is found most often in nature for silver.

Few other examples are Cr and Cu.

8 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

Read 2 more answers