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NeX [460]
3 years ago
12

What was the name of the disease that killed nearly half the people of Europe?

Chemistry
2 answers:
Licemer1 [7]3 years ago
7 0
The answer is the plague, or the black death
kaheart [24]3 years ago
5 0
Bubonic plague or black plague

You might be interested in
One of the emission spectral lines for Be3+ has a wavelength of 253.4 nm for an electronic transition that begins in the state w
4vir4ik [10]

Answer:

4

Explanation:

Relationship between wavenumber and Rydberg constant (R) is as follows:

wave\ number=R\times Z^2\frac{1}{n_1^2} -\frac{1}{n_1^2}

Here, Z is atomic number.

R=109677 cm^-1

Wavenumber is related with wavelength as follows:

wavenumber = 1/wavelength

wavelength = 253.4 nm

wavenumber=\frac{1}{253.4\times 10^{-9}} \\=39463.3\ cm^{-1}

Z fro Be = 4

39463.3=109677\times 4^2(\frac{1}{n_1^2} -\frac{1}{5^2})\\39463.3=109677\times 16(\frac{1}{n_1^2} -\frac{1}{5^2})\\n_1=4

Therefore, the principal quantum number corresponding to the given emission is 4.

6 0
3 years ago
Which of the following is true for balancing equations?
algol [13]

Answer:

A.

Explanation:

An equation with the equal amount and proportion of atoms of each element on both sides of the reaction is commonly referred to as a balanced chemical equation.

The law of conservation of matter asserts that no observable and empirical change in the amount of matter occurs within a conventional chemical process. As a result, each element in the product would have the same equal amount or numbers of atoms as the reactants.

5 0
3 years ago
The burning of magnesium is a highly exothermic reaction. How many kilojoules of heat are released when 0. 75 mol of Mg burn in
alexandr402 [8]

Taking into account the definition of enthalpy of a chemical reaction, the quantity of heat released when 0.75 moles of Mg are burned is 451.5 kJ.

<h3>Enthalpy of a chemical reaction</h3>

The enthalpy of a chemical reaction is known as the heat absorbed or released in a chemical reaction when it occurs at constant pressure. That is, the heat of reaction is the energy that is released or absorbed when chemicals are transformed into a chemical reaction.

The enthalpy is an extensive property, that is, it depends on the amount of matter present.

<h3>Heat released in this case</h3>

In this case, the balanced reaction is:

2 Mg(s) + O₂ (g) → 2 MgO(s) + 1204 kJ

This equation indicates that when 2 moles of Mg reacts with 1 mole of O₂, 1204 kJ of heat is released.

When 0.75 moles of Mg are burned, then you can apply the following rule of three: if 2 moles of Mg releases 1204 kJ of heat, 0.75 moles of Mg releases how much heat?

heat=\frac{0.75 moles of Mgx1204 kJ}{2 moles of Mg}

<u><em>heat= 451.5 kJ</em></u>

Finally, the quantity of heat released when 0.75 moles of Mg are burned is 451.5 kJ.

Learn more about enthalpy of a chemical reaction:

<u>brainly.com/question/15355361</u>

<u>brainly.com/question/16982510</u>

<u>brainly.com/question/13813185</u>

<u>brainly.com/question/19521752</u>

4 0
2 years ago
How many electrons are in the lowest occupied energy level in a Group 6A element?
kolbaska11 [484]

Answer:

2

Explanation:

4 0
3 years ago
Read 2 more answers
A cylindrical glass tube of length 27.4cm and radius 4 cm is filled with gas. The empty tube has a mass of 254.3 g. The tube fil
Temka [501]

Density of the gas is 3.05 × 10⁻³ g / cm³.

<u>Explanation:</u>

Volume of the cylinder = π r² h

where r is the radius and h is the height of the height or the length of the glass tube.

Here r = 4 cm and h = 27.4 cm

Volume of the cylinder = 3.14 × 4 × 4 × 27.4 = 1376.6 cm³

We have to find the mass of the gas by subtracting the mass of the tube filled with the substance from the mass of the empty tube.

Mass of the substance = 258.5 - 254.3 = 4.2 g

We have to find the density using the formula as,

$ Density = \frac{mass}{volume}

Plugin the values as,

$ Density = \frac{4.2}{1376.6}

              = 3.05 × 10⁻³ g / cm³

So the Density of the gas is 3.05 × 10⁻³ g / cm³.

3 0
2 years ago
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