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:
.
Answer:
# 5
Explanation:
The question describes silver being "poured" into a mold and cools to become a solid bar. This is the phase of liquid to solid. When a element cools down below it's freezing points to become a solid.
<u>Liquid to Solid Definition:</u>
Freezing, or solidification, is a phase transition in which a liquid turns into a solid when its temperature is lowered to or below its freezing point. All known liquids, except helium, freeze when the temperature is low enough.
Missing question:
A. All carbon atoms are identical.
B. An oxygen atom combines with 1.5 hydrogen atoms to form a water molecule.
C. Two oxygen atoms combine with a carbon atom to form a carbon dioxide molecule.
D. The formation of a compound often involves the destruction of one or more atoms.
Answer is: B and D.
A is correct because Daltan stated: All atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements.
C is correct because atoms combine in simple, whole- number ratios to form compounds, B is incorrect because ratio is not simple, whole number.
D is incorrect because according to Dalton. atoms can't be created or destroyed.
Answer:
Alluvial diamond mining occurs in riverbeds and beaches, where thousands of years of erosion and natural forces such as wind, rain, and water currents wash diamonds from their primary deposits in kimberlite pipes to beaches and riverbeds. Some alluvial deposits are from long-ago rivers.
When scientists say that a theory can never be proven it is always possible for a new data to contradict a theory
