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Salsk061 [2.6K]
3 years ago
5

Periodic table, chemistry questions

Chemistry
1 answer:
ehidna [41]3 years ago
7 0

Answer:

Explanation:

The Lanthanides were first discovered in 1787 when a unusual black mineral was found in Ytterby, Sweden. This mineral, now known as Gadolinite, was later separated into the various Lanthanide elements. In 1794, Professor Gadolin obtained yttria, an impure form of yttrium oxide, from the mineral.

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How many moles of potassium nitrate, KNO3 are present in a sample with a mass of 85.2 g?
Bingel [31]
0.843 moles would be the answer
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3 years ago
State the postulate of Bohr theory
KengaRu [80]

Answer:

Bohr's model of the hydrogen atom is based on three postulates:

1) An electron moves around the nucleus in a circular orbit,

2) An electron's angular momentum in the orbit is quantised,

3) The change in an electron's energy as it makes a quantum jump from one orbit to another is always accompanied by the emission or absorption of a photon. Bohr's model is semi-classical because it combines the classical concept of electron orbit (postulate 1) with the new concept of quantisation ( postulates 2 and ).

4 0
3 years ago
Arrange the following elements in order from least to greatest electronegativity:<br> Ca, F, Ne, Fe?
Burka [1]

Answer:

The electronegativity from order of least to highest is:

Ne, Ca, Fe, F

Explanation:

Elements in the periodic table have been arranged based on their level of electronegativity (which is the ability of an atom to attract electrons).

According to Paulings scale of rating elements based on their electronegativity, the electronegativity value of Fe, Ca, Ne, and F are 1.83, 1, 0 and 3.98 respectively.

Hence, based on Pauling scale, the order of electronegativity from least to highest is:

Ne > Ca > Fe > F

6 0
3 years ago
Calculate the theoretical yield for the bromination of both stilbenes
podryga [215]

Answer:

cinnamic acid - 150 mg

cis-stilbene - 100 μL

trans- stilbene - 100 mg

pyridinium tribromide - 200-385 mg

For this data:

moles of cinnamic acid = 0.150 g/148.16 g/mol = 0.001 mols

Theoretical mass of dibromoproduct formed = 0.001 mol x 307.97 g/mol = 0.312 g

cis-stilbene (100 ul = 0.1 ml)

moles of cis-stilbene = 0.1 ml x 1.01 g/mol/180.25 g/mol = 0.00056 mols

Theoretical mass of dibromoproduct formed = 0.00056 mol x 340.05 g/mol = 0.19 g

trans-stilbene

moles of tran-stilbene = 0.1 g/180.25 g/mol = 0.00055 mols

Theoretical mass of dibromoproduct formed = 0.00055 mol x 340.05 g/mol = 0.19 g

Explanation:

4 0
2 years ago
Which of the following methods can be used to completely separate a solution containing alcohol and water?
Alenkinab [10]
A only gets out some of it but not all
C that isn't for alcaholl
D I don't think that even exists
B is the only correct answer
6 0
3 years ago
Read 2 more answers
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