Answer:
Pure substance: sugar
A chemical change: occurs when methane is burned.
Explanation:
Pure substances have definite <em>constant compositions</em> (reflected in formulas) and have their own <em>chemical properties</em>. On the other hand, mixtures are made of two or more pure substances (<em>variable composition</em>) and their chemical properties depend on each combination. From the list, only sugar is a pure substance (C₁₂H₂₂O₁₁), whereas seawater, air, lemonade, and milk are mixtures.
Chemical changes (chemical reactions) occur when pure substances transform into others, and therefore there are new formulas. Conversely, in physical changes, pure substances <em>preserve their identity</em> (formula) but have changes in their <em>physical properties</em>. Methane being burned is a chemical change since new substances are formed:
CH₄ + O₂ ⇄ CO₂ + H₂O
Water vaporization, paper shredding and dissolution of solids in liquids are examples of physical changes.
Answer:
The answer is Diffusion.
Explanation:
Diffusion is a movement of molecules(substances) from a region of high concentration to a region of low concentration down a concentration gradient.
Explanation:
Given parameters:
Wavelength of photon = 1.95 x 10⁻¹¹m
Unknown:
Frequency of the wave = ?
Energy of the photon = ?
Solution:
The frequency and wavelength of a wave are related by the expression;
C = Fλ
C = speed of light = 3 x 10⁸m/s
F = frequency
λ = wavelength
Insert the parameters and solve;
3 x 10⁸ = F x 1.95 x 10⁻¹¹
F = 
= 1.54 x 10¹⁹Hz
Energy of the photon is related to frequency using the expression below;
E = hF
h is the Planck's constant = 6.634 x 10⁻³⁴m²kg/s
Insert the parameters and solve;
E = 6.634 x 10⁻³⁴ x 1.54 x 10¹⁹ = 1.02 x 10⁻¹⁴J
Answer:
93.15 %
Explanation:
We have to start with the chemical reaction:
Now, we can balance the reaction:
Our initial data are the 15.71 g of 
, so we have to do the following steps:
1) <u>Convert from grams to moles of using the molar mass (110.98 g/mol).</u>
2) <u>Convert from moles of to moles of 
using the molar ratio. ( 1 mol = 1 mol of ).</u>
3) <u>Convert from moles of to grams of using the molar mass. (100 g/mol).</u>
Finally, we can calculate the yield percent:
I hope it helps!
