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3 years ago

For question #12, use the following picture: 12. What element is this? How do you know?

Chemistry

2 answers:

labwork [276]3 years ago

8 0

Answer: The element shown in the image is Helium (He).

Explanation: We are given a image of an atom having protons, neutrons and electrons.

Number of protons as shown in image = 2

Number of neutrons as shown in image = 2

Number of electron as shown in image = 2

Atomic number = Number of protons = Number of electrons

Atomic number of the element = 2

Atomic Mass = Number of protons + Number of neutrons

Atomic mass = 2 + 2 = 4

The element having Atomic number = 2 and mass number = 4 is Helium.

Element = $^4_2\textrm{He}$

morpeh [17]3 years ago

3 0

I believe the element is Helium. I know this because an atom of helium has an atomic number of 2, meaning it has 2 protons. Because it is an atom of helium and not an ion of helium it also possess the same number of electrons as well which is 2.

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tino4ka555 [31]

Answer: The mass percentage of $Tl_2SO_4$ is 5.86%

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To calculate the mass percentage of $Tl_2SO_4$ in the sample it is necessary to know the mass of the solute ( $Tl_2SO_4$ in this case), and the mass of the solution (pesticide sample, whose mass is explicit in the letter of the problem).

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3 years ago

if 5430 J of energy is used to heat 1.25 L of room temp. water (23.0 °C) whats the final temp of the water?

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We can use the heat equation,
Q = mcΔT

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Density = mass / volume

The density of water = 0.997 g/mL

Hence mass of 1.25 L (1250 mL) of water = 0.997 g/mL x 1250 mL

= 1246.25 g

Specific heat capacity of water = 4.186 J/ g °C.

Let's assume that there is no heat loss to the surrounding and the final temperature is T.

By applying the equation,

5430 J = 1246.25 g x 4.186 J/ g °C x (T - 23) °C
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