Answer:
3.75 g.
Explanation:
<em>mass percent is the ratio of the mass of the solute to the mass of the solution multiplied by 100.</em>
<em />
<em>mass % = (mass of solute/mass of solution) x 100.</em>
<em></em>
mass of calcium nitrite = ??? g,
mass of the solution = 25.0 g.
∴ mass % = (mass of solute/mass of solution) x 100
<em></em>
<em>∴ mass of solute (calcium nitrite) = (mass %)(mass of solution)/100</em> = (15.0 %)(25.0 g)/100 = <em>3.75 g.</em>
An exothermic reaction is a type of chemical reaction in which energy is released to the environment in form of heat or light. Endothermic reaction in the other hand is a chemical reaction where energy is taken from the surroundings and thus the surroundings end up with less energy than they started with. In this case; the above reaction is an Exothermic reaction (heat is being released to the surroundings).
Periodic table is an arrangement of chemical elements in an organized manner with atomic number. Elements are distributed in columns and groups in periodic table according to their properties.
Many elements have their isotopes and mostly are radioactive but isotopes are not mentioned on the periodic table, elements are mentioned there and all trans-uranium elements are most radioactive.
Answer:
There are three significant problems:
The Flatness Problem:
WMAP has determined the geometry of the universe to be nearly flat. However, under Big Bang cosmology, curvature grows with time. A universe as flat as we see it today would require an extreme fine-tuning of conditions in the past, which would be an unbelievable coincidence.
The Horizon Problem:
Distant regions of space in opposite directions of the sky are so far apart that, assuming standard Big Bang expansion, they could never have been in causal contact with each other. This is because the light travel time between them exceeds the age of the universe. Yet the uniformity of the cosmic microwave background temperature tells us that these regions must have been in contact with each other in the past.
The Monopole Problem:
Big Bang cosmology predicts that a very large number of heavy, stable "magnetic monopoles" should have been produced in the early universe. However, magnetic monopoles have never been observed, so if they exist at all, they are much more rare than the Big Bang theory predicts.
