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2 years ago

Social Studies 3rd Period

Chemistry

1 answer:

docker41 [41]2 years ago

7 0

Answer:

The answer is A, B, and D

Explanation:

A: China burned coal more than wood for heat.

B: Marco Polo wrote about a new energy source from China.

D: Marco Polo helped spread technology and ideas all through out Europe.

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Nitrogen dioxide is a red-brown gas responsible for the brown color of smog. A container of nitrogen dioxide that is at low pres

____ [38]

Answer:

Initially $1.51\times 10^{-2} moles$ of nitrogen dioxide were in the container .

Explanation:

Volume of the container at low pressure and at room temperature = $V_1=3.4 L$

Number of moles in the container = $n_1$

After more addition of nitrogen gas at the same pressure and temperature.

Volume of the container after addition = $V_2=5.11 L$

Number of moles in the container after addition= $n_2=2.28\times 10^{-2} mol$

Applying Avogadro's law:

$\frac{Volume}{Moles}=constant$ (at constant pressure and temperature)

$\frac{V_1}{n_1}=\frac{V_2}{n_2}$

$n_1=\frac{V_1\times n_2}{V_2}=\frac{3.4 L\times 2.28\times 10^{-2} mol}{5.11 L}$

$n_1=1.51\times 10^{-2} mol$

Initially $1.51\times 10^{-2} moles$ of nitrogen dioxide were in the container .

8 0

3 years ago

A sample of 28 Mg decays initially at a rate of 53500 disintegrations per minute, but the decay rate falls to 10980 disintegrati

prisoha [69]

Answer : The half life of 28-Mg in hours is, 6.94

Explanation :

First we have to calculate the rate constant.

Expression for rate law for first order kinetics is given by:

$k=\frac{2.303}{t}\log\frac{a}{a-x}$

where,

k = rate constant

t = time passed by the sample = 48.0 hr

a = initial amount of the reactant disintegrate = 53500

a - x = amount left after decay process disintegrate = 53500 - 10980 = 42520

Now put all the given values in above equation, we get

$k=\frac{2.303}{48.0}\log\frac{53500}{42520}$

$k=9.98\times 10^{-2}hr^{-1}$

Now we have to calculate the half-life.

$k=\frac{0.693}{t_{1/2}}$

$9.98\times 10^{-2}=\frac{0.693}{t_{1/2}}$

$t_{1/2}=6.94hr$

Therefore, the half life of 28-Mg in hours is, 6.94

8 0

3 years ago

How would Bohr model show the protons in a carbon atom

MariettaO [177]

Answer:

The Bohr model show the protons in a carbon atom using the model; "Electrons move in fixed orbits around a nucleus of protons and neutrons."

According to Bohr's model of the atoms, the Rutherford model is basically correct. This implies that Bohr model accepts the idea of a nucleus containing nucleons(protons and neutrons).

In addition, the model also postulates that electrons are found in fixed orbits. These fixed orbits are called energy levels or shells.

A graphic description of this is shown in the image attached to this answer.

Learn more: brainly.com/question/3964366

Explanation:

6 0

2 years ago

At a certain temperature the vapor pressure of pure methanol is measured to be . Suppose a solution is prepared by mixing of met

CaHeK987 [17]

Answer:

Partial pressure is 0.13 atm

Explanation:

CHECK THE COMPLETE QUESTION BELOW :

At a certain temperature, the vapor pressure of pure methanol is measured to be 0.43atm. Suppose a solution is prepared by mixing 88.2 g of methanol and 116.g of water. Calculate the partial pressure of methanol vapor above this solution. Be sure your answer has the correct number of significant digits. Note for advanced students: you may assume the solution is ideal.

Using Raoult´s law for ideal soultions we have

P(A) = X(A) *Pº(A)

where P(A) is the partial vapor pressure pressure of methanol,

X(A) is the mole fraction of solute (methanol) in solution,

Pº(A) is the vapor pressure of pure solute

Raoult's law states that the vapor pressure of a solution is dependent on the mole fraction of a solute added to the solution.

Raoult's law can be expressed below

Psolution = ΧsolventP0solvent.

Expressing it interns of the constituents given in the question we have

P(CH₃OH) = X(CH₃OH) x Pº(CH₃OH)

To calculate the mole fraction of CH₃OH, we make use of the formula below :

X(A) = mol (A) / ntotal

Ntotal = (sum of number of moles of A )+( moles solvent)

mol (CH₃3OH) can be calculated as :: 88.2 g/ 32 g/mol = 2.76 mol of CH₃OH

mol (H₂O) can be calculated as ::116 g/ 18 g/mol = 6.44 mol

total n = (6.44 + 2.76) mol = 9.20 mol

To calculate the partial pressure the we say;

P(CH₃OH) = (2.76 mol CH + 9.20 mol) x( 0.43 atm) = 0.13 atm

Hence, the partial pressure rounded to two significant figures is 0.13 atm

8 0

3 years ago

A nonmetal

mars1129 [50]

$^{16}_{\phantom{1}8}\text{O}$ .

Oxygen-16 is the atom in question.

Atomic number: 8.
Mass number: 16.

<h3>Explanation</h3>

The superscript of the ion says "2-". That means that the ion here carries a charge of -2.

The charge is negative, meaning that there are more electrons (which are negative) than protons (which are positive) in that ion.
The size of the charge is 2. There are two more electrons than protons in that ion.

There are 10 electrons in total in that ion. There are two more electrons than protons. That means that there are 10 - 2 = 8 protons in that ion.

The atomic number of an atom is the same as its number of protons. The atomic number of X is 8.

The atomic number determines the element. Atomic number 8 is oxygen. Thus element X is oxygen.

Mass number is the sum of number of protons and neutrons in an atom. 8 + 8 = 16 for this atom.

5 0

3 years ago