Ughhh ughh ughhhh helppp

Which statements accurately describe Dmitri Mendeleev’s contributions to the development of the periodic table? Check all that a

Varvara68 [4.7K]

Answer:

Mendeleev produced the first orderly arrangement of known elements.

Mendeleev used patterns to predict undiscovered elements.

Explanation:

Mendeleev produced the first orderly arrangement of known elements and used patterns to predict the undiscovered elements.

Those two statments are true.

For the time being there were some 62 known elements. Before Medeleev some schemes to order part of the elements were proposed, but Medeleev showed the relationship between the atomic mass and the properties of the elements (supports second choice). This arrangement is known as the periodic table.

More importantly, Mendeleev predicted correctly the existance and properties of unknown elements, which is his major contribution: he left blanket spaces which where gradually filled when new elements where discovered (this supports the fourth choice).

The first modern chemistry book was written by Antoine Lavoisier (this discards first option).

Mendeleev ordered the elements by increasing mass number (this discards third choice), which was corrected later by the scientist Henry Moseley, who ordered the elements by increasing atomic number (number of protons).

Isotopes were not known by Mendeleev times, so this discards the last option.

8 0

3 years ago

Read 2 more answers

The volume of a given mass of an ideal gas at constant pressure is

zmey [24]

Answer:

inversely proportional to the kelvin temperature

Explanation:

PV=nRT

8 0

3 years ago

Read 2 more answers

Calculate the freezing point (in degrees C) of a solution made by dissolving 7.99 g of anthracene{C14H10} in 79 g of benzene. Th

mario62 [17]

Answer: The freezing point of solution is 2.6°C

Explanation:

To calculate the depression in freezing point, we use the equation:

$\Delta T_f=iK_fm$

Or,

$\Delta T_f=i\times K_f\times \frac{m_{solute}\times 1000}{M_{solute}\times W_{solvent}\text{ in grams}}$

where,

$\Delta T_f$ = $\text{Freezing point of pure solution}-\text{Freezing point of solution}$

Freezing point of pure solution = 5.5°C

i = Vant hoff factor = 1 (For non-electrolytes)

$K_f$ = molal freezing point depression constant = 5.12 K/m = 5.12 °C/m

$m_{solute}$ = Given mass of solute (anthracene) = 7.99 g

$M_{solute}$ = Molar mass of solute (anthracene) = 178.23 g/mol

$W_{solvent}$ = Mass of solvent (benzene) = 79 g

Putting values in above equation, we get:

$5.5-\text{Freezing point of solution}=1\times 5.12^oC/m\times \frac{7.99\times 1000}{178.23g/mol\times 79}\\\\\text{Freezing point of solution}=2.6^oC$

Hence, the freezing point of solution is 2.6°C

8 0

3 years ago

For the following reaction, identify the element that was oxidized, the element that was reduced, and the reducing agent. Give a

Volgvan

For this reaction, oxidation number of Carbon in CO would be +2 while oxidation number of carbon in CO2 would be +4 and so this means that carbon has oxidized. Oxidation number of nitrogen in NO is +2. While oxidation number of nitrogen in N2 is 0 so this means that nitrogen had reduced. The reducing agent is the one which provides electrons by oxidizing itself so in this case; CO is the reducing agent while the C in CO oxidized to produce electrons. I am hoping that this answer has satisfied your query about and it will be able to help you, and if you’d like, feel free to ask another question.

6 0

3 years ago

¿Cuántos electrones conforman un enlace doble?

Aleks04 [339]

Answer:

Cada átomo aporta dos electrones al enlace, es decir, se comparten dos pares de electrones entre dos átomos. Un ejemplo es la molécula de Oxígeno (O2).

Explanation:

6 0

3 years ago

Ughhh ughh ughhhhhelppp​

Ughhh ughh ughhhhhelppp