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balu736 [363]
4 years ago
5

What element is this? How do you know?

Chemistry
1 answer:
Gnom [1K]4 years ago
8 0

This element is Helium. This is because it has two protons and two neutrons in its nucleus. this makes it have the atomic mass of approximately four atomic mass units. It also has two electrons in the first energy level. . It is therefore a noble gas since this is the only energy level and it obeys the 2n² rule for the filling of energy levels. n in this case is 1 making the maximum number of electrons in the first energy level to be 2.

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A 2.600×10−2 M solution of glycerol (C3H8O3) in water is at 20.0∘C. The sample was created by dissolving a sample of C3H8O3 in w
sesenic [268]

Answer:

A. 0.2395 w/w %

B. 2394ppm

Explanation:

A. To find concentrationin percent by mass of the solution we need to calculate mass of glycerol and mass of water. The formula is:

Mass glycerol / Total mass * 100

<em>Mass glycerol:</em>

The solution is 2.6x10⁻²moles / L. As there is 1L of solution there are 2.6x10⁻² moles of glycerol. In mass (Using molar mass glycerol: 92.09g/mol):

2.6x10⁻² moles of glycerol * (92.09g / mol) = 2.394g glycerol

<em>Mass of water:</em>

998.9mL and density = 0.9982g/mL:

998.9mL * (0.9982g/mL) = 997.1g of water.

That means percent by mass is:

% by mass: 2.394g / (997.1g + 2.394g) * 100 = 0.2395 w/w %

B. Parts per million are mg of glycerol per L of solution. As in 1L there are 2.394g. In mg:

2.394g * (1000mg / 1g) = 2394mg:

Parts per million: 2394mg / L = 2394ppm

3 0
3 years ago
Each Excedrin tablet contains 250 mg aspirin (ACE), 250 mg of acetaminophen (ACE), and 65 mg of caffeine (CAF). Calculate the th
yawa3891 [41]

Answer:

a) 37.04%  b) 37.04%  c) 9.63%

Explanation:

The theoretical percent recovery (Tr), is the total percentage of each compound in the sample. Depending on the technique used to recovery the compounds, the percent recovery will be less than the theoretical, because no technique is 100% efficient.

So, to calculate the theoretical, it will be the mass of the compound divided by the mass of the sample multiplied by 100%.

a) Tr = (250 mg)/(675 mg) * 100%

Tr = 37.04%

b) Tr = (250 mg)/(675 mg) * 100%

Tr = 37.04%

c) Tr = (65 mg)/(675 mg) * 100%

Tr = 9.63%

3 0
4 years ago
Wich reason is the best for choosing the ruler to measure the dimensionof tbe wooden block
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7 0
4 years ago
Explain how to use the displacement method to find the volume of an object?
DENIUS [597]
<span>A submerged object displaces a volume of liquid equal to the volume of the object. One milliliter (1 mL) of water has a volume of 1 cubic centimeter (1cm3).</span>
3 0
3 years ago
When Rutherford's coworkers bombarded gold foil with a particles, they obtained results that overturned the existing (Thomson) m
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Explanation:

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Rutherford conducted an experiment in which he took a thin gold particle film on which he passes alpha- particles. He noticed that:

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He concluded that:

Most of space of atom is empty and in center of atom , there is solid mass which is cause of alpha particles to come back. He gave term nucleus to this solid mass.

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