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jarptica [38.1K]
3 years ago
9

Descibe the probable causes of two mass extinctions.

Chemistry
1 answer:
andrew11 [14]3 years ago
7 0
Humans of course this is obvious. With all the things going on I wouldn't be surprised if we die of pollution. And of course the Javan Gorilla there are only about 60 that still exist!
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Five physical properties of ionic compounds
ipn [44]

Answer:

what is ionic? Is it iron

Explanation:

4 0
3 years ago
How is the mole of a used to express the mass of a substance explain​
diamong [38]

Answer:

See explanation

Explanation:

The mole refers to the amount of substance contained in 12 g of carbon-12. It was arbitrarily related to the number of elementary entities in 12 g of carbon -12 by Prof. Avogadro.

The number of moles of a substance is obtained as the mass of the substance divided by the mass of one mole of the substance (molar mass). Hence when the number of moles is known, the mass is now;

number of moles * molar mass

8 0
3 years ago
A sample that weighs 103.75 g is a mixture of 30% helium atoms and 70% krypton atoms. How many particles are present in the samp
aalyn [17]
1) we calculate the molar mass of He (helium) and Kr (Krypton).
atomic mass (He)=4 u
atomic mas (Kr)=83.8 u

Therefore the molar mass will be:
molar mass(He)=4 g/mol
molar mass(Kr)=83.8 g/mol.

1) We can find  the next equation:
mass=molar mass  x number of moles.

x=number of moles of helium
y=number of moles of helium. 

(4 g/mol) x  +(83.8 g/mol)y=103.75 g
Therefore, we have the next equation:

(1)

4x+83.8y=103.75


2) We can find other equation:

We have 30% helium atoms and 70% Kryptum atoms, therefore we have 30% Helium moles and 70% of Krypton moles.

1 mol  is always 6.022 * 10²³ atoms or molecules, (in this case atoms).

Then:
x=number of moles of helium
y=number of moles of helium.
(x+y)=number of moles of our sample.

x=30% of (x+y)

Therefore, we have this other equation:
(2)

x=0.3(x+y)


With the equations(1) and (2), we have the next system of equations:

4x+83.8y=103.75

x=0.3(x+y)  ⇒ x=0.3x+0.3y  ⇒    x-0.3x=0.3y  ⇒ 0.7 x=0.3y ⇒ x=0.3y/0.7
⇒x=3y/7

We solve this system of equations by substitution method.
x=3y/7

4(3y/7)+83.8y=103.75
lower common multiple)7
12y+586.6y=726.25
598.6y=726.25
y=1.21

x=3y/7=3(1.21)/7=0.52

We have 0.52 moles of  helium and 1.21 moles of Krypton.

1 mol=6.022 * 10²³ atoms

Total number of particles=(6.022 *10²³ atoms /1 mol) (number of moles of He+ number of moles of Kr).

Total number of particles=6.022 * 10²³ (0.52+1.21)=6.022 * 10²³ (1.73)=
=1.044 * 10²⁴ atoms.

Answer: The sample have 1.044 * 10²⁴ atoms.
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Heat would best be transferred by conduction between
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A stove and a copper pot
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Which of the following is an example of the endocrine system maintaining homeostasis?
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Answer:Releasing insulin to decrease blood sugar and releasing glucagon to increase blood sugar

Explanation: homoestasis is the process by which the body keep it's internal environment constant, regardless of change in the external environment. The human body has a normal range in which it's system operates and it uses homoestasis to keep these at constant.

Homeostasis could be positive or negative. It usually involves a sensor which detects the changes in the body and passes the information to the control center, a control center which receive information from the sensor and sends signals to the effectors and the effector which acts on the information sent by the control center to effect normalcy.

In this case, when a person eats food,he gets glucose. Blood sugar most be kept at constant so the endocrine system release the hormone insulin. Insulin helps to convert glucose to glycogen, which is the form it can be stored in the liver

When the blood sugar levels is low, the brain which is the control center causes glucagon to be released . This hormone converts glycogen to glucose

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