Answer:
Approximately 75%.
Explanation:
Look up the relative atomic mass of Ca on a modern periodic table:
There are one mole of Ca atoms in each mole of CaCO₃ formula unit.
- The mass of one mole of CaCO₃ is the same as the molar mass of this compound:
. - The mass of one mole of Ca atoms is (numerically) the same as the relative atomic mass of this element:
.
Calculate the mass ratio of Ca in a pure sample of CaCO₃:
.
Let the mass of the sample be 100 g. This sample of CaCO₃ contains 30% Ca by mass. In that 100 grams of this sample, there would be 
of Ca atoms. Assuming that the impurity does not contain any Ca. In other words, all these Ca atoms belong to CaCO₃. Apply the ratio 
:
.
In other words, by these assumptions, 100 grams of this sample would contain 75 grams of CaCO₃. The percentage mass of CaCO₃ in this sample would thus be equal to:
.
Carbon dioxide, or
, is a pure covalent bond.
pure - it's non-polar, because it's a linear & symmetrical bond.
covalent - covalence is when 2 electrons are shared by a pair of atoms. in the case of carbon dioxide, it's three atoms with an oxygen atom on the right, an oxygen atom on the left, and a carbon atom smack in the middle. 2 of carbon's extra electrons are shared with the right oxygen, and 2 other extra atoms are shared with with left oxygen.
Answer:
Explanation:
Cyanobacteria, also known as blue-green algae, are a kind of bacteria found in many lakes. These organisms make their own food through photosynthesis. Small animals, including mayfly larvae, eat the cyanobacteria. ... The small fish provide food for larger fish, such as walleye.
<span>The correct answer here is that the reason chemical changes can be considered unseen, is because the alterations made within an element when it undergoes a chemical change occurs within the very atoms of the cell itself. In contrast with this, a physical change (such as a solid changing to a liquid through melting) does not change the element itself, but just it's physical form, so this can be seen easily to the human eye.</span>
Answer:
And that means fish must be able to survive down here. This is due to a special property of water: the elasticity of H2O. We know that when the temperature sinks below freezing, water first contracts and then expands as it begins to turn to ice. Ice, being lighter than water, floats.
Explanation:
The property of water that allows fish to survive in a lake that is frozen over is the fact that ice is less dense than liquid water.
