Answer:
The spectra of the Sun and stars exhibited bright and dark lines called Fraunhofer lines. These were shown to be caused by elements emitting or absorbing light at specific wavelengths. Because each element emits or absorbs light only at specific wavelengths, the chemical composition of stars can be determined.
KOH -------> K+ OH-
Ba(OH)2 ------> Ba+2. 2OH-
Answer:
"Freezing point and ability to react with oxygen" are chemical properties
Explanation:
The change of liquid into solid is the freezing point. The melting point is more than the freezing point in certain cases of mixtures for certain organic compounds like fats. As soon as the mixture freezes it becomes solid and which results in change in the composition from the liquid and solid in this way the it drastically reduces the freezing point. The melting point gets higher due to the pressure. This happens due to the release of heat of which results in the rise of temperature to the freezing point
.Also the reaction of elements with oxygen which leads to formation of new substance is also an chemical property
Answer:The mole is important because it allows chemists to work with the subatomic world with macro world units and amounts. Atoms, molecules and formula units are very small and very difficult to work with usually. However, the mole allows a chemist to work with amounts large enough to use.
Explanation:
Complete question is;
A drop of water has a volume of approximately 7 × 10⁻² ml. How many water molecules does it contain? The density of water is 1.0 g/cm³.
This question will require us to first find the number of moles and then use avogadro's number to get the number of water molecules.
<em><u>Number of water molecules = 2.34 × 10²¹ molecules</u></em>
We are given;
Volume of water; V = 7 × 10⁻² ml
Density of water; ρ = 1 g/cm³ = 1 g/ml
Formula for mass is; m = ρV
m = 1 × 7 × 10⁻²
m = 7 × 10⁻² g
from online calculation, molar mass of water = 18.01 g/mol
Number of moles(n) = mass/molar mass
Thus;
n = (7 × 10⁻²)/18.01
n = 3.887 × 10⁻³ mol
from avogadro's number, we know that;
1 mol = 6.022 × 10²³ molecules
Thus,3.887 × 10⁻³ mol will give; 6.022 × 10²³ × 3.887 × 10⁻³ = 2.34 × 10²¹ molecules
Read more at; brainly.in/question/17990661
