In 1869 he published a table of the elements organized by increasing atomic mass.
Mendeleev is called the "father of the modern periodic table
stated that if the atomic weight of an element caused it to be placed in the wrong group, then the weight must be wrong. (He corrected the atomic masses of Be, In, and U)
was so confident in his table that he used it to predict the physical properties of three elements that were yet unknown.
After the discovery of these unknown elements between 1874 and 1885, and the fact that Mendeleev's predictions for Sc, Ga, and Ge were amazingly close to the actual values, his table was generally accepted.
However, in spite of Mendeleev's great achievement, problems arose when new elements were discovered and more accurate atomic weights determined.
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Answer:
23.6 moles
Explanation:
From the question given above, the following data were obtained:
Mass of air = 3.6 Kg
Mass percentage of O₂ = 21%
Number of mole of O₂ =?
Next, we shall convert 3.6 Kg of air to grams (g). This can be obtained as follow:
1 kg = 1000 g
Therefore,
3.6 Kg = 3.6 Kg × 1000 / 1 kg
3.6 Kg = 3600 g
Next, we shall determine the mass of O₂ in the air. This can be obtained as follow:
Mass of air = 3600 g
Mass percentage of O₂ = 21%
Mass of O₂ =?
Mass of O₂ = 21% × 3600
Mass of O₂ = 21/100 × 3600
Mass of O₂ = 756 g
Finally, we shall determine the number of mole of O₂ in the sample of air. This can be obtained as follow:
Mass of O₂ = 756 g
Molar mass of O₂ = 2 × 16 = 32 g/mol
Number of mole of O₂ =?
Mole = mass /Molar mass
Number of mole of O₂ = 756 / 32
Number of mole of O₂ = 23.6 moles
Thus, the number of mole of O₂ in the
sample of air is 23.6 moles
Answer:
a. True
Explanation:
Palmitic acid is the acid found in animals and plants. It is the saturated acid that contains fats. It is extracted from palm oil and from fat sources like butter, cheese, milk and meat. It is added in milk with low fat content to add Vitamin A in it. The fat content of palmitic acid is very high. excessive consumption of palmitic acid leads to heart diseases and life risks.
<span>A pure substance contains only one kind of molecule, and a mixture is a combination of two or more pure substances.</span>
Answer: 24.1%, under below assumptions.
Justification:
The question is quite ambiguous, because one of the data is not clearly stated. It says that the mixture consists on two compounds:
- sodium bicarbonate, and
- ammonium bicarbonate
.After, it says that it is 75.9 % bicarbonate, but it does not specify which bicarbonate, it might be the sodium bicarbonate or the ammonium bicarbonate. It is apparent that you omitted that information by error.
Given that later, the question is <span>what the mass percent of sodium bicarbonate is in the mixture, it is supposed that the 75.9% content is of ammonium bicarbonate.
With that said, you can calculate the mass percent of sodium bicarbonate, because there are only two compounds and so you know that both add up the 100% of the mixture.
In formulas:
100% = %m/m sodium bicarbonate + %m/m ammonium bicarbonate = 100%
=> % m/m sodium bicarbonate = 100% - % m/s ammonium bicarbonate
=> % sodium bicarbonate = 100% - 75.9% = 24.1%
Answer: 24.1%
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