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2 years ago

A balloon contains 7.36 g of oxygen gas (O2). How many oxygen molecules are in the balloon?

1 answer:

7 0

Avagadros constant states that 1 mol of any substance is made of 6.022 x 10^23 units.
These units could be atoms making up elements or molecules making up compounds.
1 mol of molecular oxygen (O2) is made of 6.022 x 10^23 molecules of O2
The mass of 1 mol of O2 is 32 g/mol
This means that the number of oxygen molecules in 32 g are 6.022 x 10^23 molecules
Therefore in 7.36 g of oxygen gas there are - 6.022 x 10^23 /32 g/mol x 7.36 g = 1.39 x 10^23 oxygen molecules
Answer is 1.39 x 10^23 oxygen molecules

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A solution is prepared by adding 6.24 g of benzene (C 6H 6, 78.11 g/mol) to 80.74 g of cyclohexane (C 6H 12, 84.16 g/mol). Calcu

tekilochka [14]

Answer:

$x_B=0.0769$

$m=0.990m$

Explanation:

Hello,

In this case, we can compute the mole fraction of benzene by using the following formula:

$x_B=\frac{n_B}{n_B+n_C}$

Whereas n accounts for the moles of each substance, thus, we compute them by using molar mass of benzene and cyclohexane:

$n_B=6.24g*\frac{1mol}{78.11g}=0.0799mol\\ \\n_C=80.74g*\frac{1mol}{84.16g} =0.959mol$

Thus, we compute the mole fraction:

$x_B=\frac{0.0799mol}{0.0799mol+0.959mol}\\ \\x_B=0.0769$

Next, for the molality, we define it as:

$m=\frac{n_B}{m_C}$

Whereas we also use the moles of benzene but rather than the moles of cyclohexane, its mass in kilograms (0.08074 kg), thus, we obtain:

$m=\frac{0.0799mol}{0.08074kg}=0.990mol/kg$

Or just 0.990 m in molal units (mol/kg).

Best regards.

7 0

2 years ago

The highest principal enegy level of period 2 elements is 2. Period 3 elements all have six 3p electrons. Period 4 elements have

Dmitrij [34]

Explanation:

The highest principal energy level of period 2 elements is 2. (True)

The highest principle energy level of elements of any period is equal to period number. So the given statement is true.

Period 3 elements all have six 3p electrons – (False)

For example, sodium and sulfur are period 3 elements but do not contain six 3p electrons. Only Argon of period possesses six p-electrons.

Period 4 elements have an inner electron configuration of [Ar]- (True)

Atomic number of elements belonging to period 4 have atomic number more than 18 (atomic number of Ar). So they must have an inner electron configuration of [Ar]

The valence electrons of group 5A elements are in the 6s subshell – [FALSE]

Elements of group 5A are nitrogen, arsenic, antimony and bismuth. They are p-block elements. Therefore, valence electrons are present in p-subshell.

Group 8A elements have full outer principal s and p subshells –(True)

Group 8A elements are also known as noble gas element. Octets of noble gases are complete and hence, have full outer principal s and p subshells.

The valence electrons of group 2A elements are in an s subshell – (True)

Elements of group 2A are barium, magnesium, calcium, etc. They belong to s-block elements. Therefore, their valence electrons will be in s-subshell.

The highest principal energy level of period 3 elements is 4 – (False)

The highest principle energy level of elements of any period is equal to period number.

For example, sodium is present in 3rd period, so its principle quantum number will be 3.

Period 5 elements have an inner electron configuration of [Xe] – (False)

Period 5 elements have an inner electron configuration of [Kr]. The first member of this period is rubidium. 37 and that of Kr is 36.

6 0

2 years ago

<img src="https://tex.z-dn.net/?f=PCl_5%20%5Crightleftarrows%20PCl_3%20%2B%20Cl_2" id="TexFormula1" title="PCl_5 \rightleftarrow

Butoxors [25]

<u>Answer:</u> The total pressure of the container will be 2.00 atm

<u>Explanation:</u>

We are given:

Initial moles of phosphorus pentachloride = 1.00 atm

For the given chemical reaction:

$PCl_5\rightleftharpoons PCl_3+Cl_2$

By Stoichiometry of the reaction:

1 mole of $PCl_5$ produces 1 mole of $PCl_3$ and 1 mole of chlorine gas

So, 1.00 atm of $PCl_5$ will also produce 1.00 atm of $PCl_3$ and 1.00 atm of chlorine gas when the reaction goes to completion.

Total pressure of the container when the reaction goes to completion = 1.00 + 1.00 = 2.00 atm

Hence, the total pressure of the container will be 2.00 atm

3 0

2 years ago

A 85.2 g copper bar was heated to 221.32 degrees Celsius and placed in a coffee cup calorimeter containing 4250 mL of water at 2

VLD [36.1K]

Answer:- 64015 J

Solution: There is 4250 mL of water in the calorimeter at 22.55 degree C.

density of water is 1 g per mL.

So, the mass of water = $4250mL(\frac{1g}{1mL})$ = 4250 g

Final temperature of water after adding the hot copper bar to it is 26.15 degree C.

So, $\Delta T$ for water = 26.15 - 22.55 = 3.60 degree C

Specific heat for water is 4.184 $\frac{J}{g.^0C}$

The heat gained by water is calculated by using the formula:

$q=mc\Delta T$

where, q is the heat energy, m is mass and c is specific heat.

Let's plug in the values in the formula and do the calculations:

$q=4250g*\frac{4.184J}{g.^0C}*3.60^0C$

q = 64015 J

So, 64015 J of heat is gained by the water.

5 0

2 years ago

Nuclear power plants produce energy using fission. One common fuel, uranium-235, produces energy through the fission reaction 23

Vikentia [17]

Answer:

mass of U-235 = 15.9 g (3 sig. figures)

Explanation:

1 atom can produce -------------------------> 3.20 x 10^-11 J energy

x atoms can produce ----------------------> 1.30 x 10^12 J energy

x = 1.30 x 10^12 / 3.20 x 10^-11

x = 4.06 x 10^22 atoms

1 mol ----------------------> 6.023 x 10^23 atoms

y mol ----------------------> 4.06 x 10^22 atoms

y = 0.0675 moles

mass of U-235 = 0.0675 x 235 = 15.8625

mass of U-235 = 15.9 g (3 sig. figures)

7 0

2 years ago