If a sound wave refracts,It changes its speed and wavelength when it bounces off of a solid surface,It changes its speed and wavelength when it passes through an opening, and It changes direction when it passes from one medium to another. Therefore, option A, C and D are correct.
An important case in which sound waves change form or spread out is called refraction. This phenomenon affects the bending of a sound wave owing to changes in the wave's speed.
Refraction is the reason ocean waves near a shore parallel to the beach and why glass lenses can be used to focus light waves.
If the air above the earth is warmed than that at the surface, sound will be change shape back downward toward the surface by refraction. Soundpropagates in all directions from a point source.
Thus, option A, C and D are correct.
To learn more about the refraction of sound wave, follow the link;
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Answer: option (3) SrO, with 84.56%
Explanation:
You have to calculate the mass of strontium and the mass of the compound, for each of the four compounds, and compute the percent:
percent of strontium = (mass of strontium / mass of the chemical formula) × 100 %.
These are the atomic masses of the elements that you have to use:
Atomic mass of Sr: 87.62 g/mol
Atomic mass of Cl: 35.453 g/mol
Atomic mass of I: 126.904 g/mol
Atomic mass of O: 15.999 g/mol
Atomic mass of S: 32.065 g/mol
(1) SrCl₂:
i) mass of Sr: 87.62 g/mol
ii) mass of Cl₂: 2×35.453 g/mol = 70.906 g/mol
iii) mass of SrCl₂: 87.62 g/mol + 70.906 g/mol = 158.526 g/mol
iv) Sr % = [87.62 / 158.526 ] × 100 = 55.27%
(2) SrI₂
Following the same procedure:
i) Sr % = [87.62 / (87.62 + 2× 126.904) ] × 100 = 25.66%
(3) SrO
i) Sr % = [87.62 / (87.62 + 15.999) ] × 100 = 84.56%
(4) SrS
i) Sr % = [87.62 / (87.62 + 32.065) ] × 100 = 73.21%
b. decreases across a period but increases down a group.
c. increases across a period but decreases down a group.
d. decreases across a period and decreases down a group.
Which statement is true about energy in this reaction?
(1) The reaction is exothermic because it releases heat.
(2) The reaction is exothermic because it absorbs heat.
(3) The reaction is endothermic because it releases heat.
(4) The reaction is endothermic because it absorbs heat.
Answer: The answer is (2) the reaction is exothermic because it releases heat.