Humans knowingly create environmental disasters?
Answer:
Amount left after 25 days = 12.5 g
Explanation:
Given data:
Mass of sample = 400 g
Half life of sample = 5 days
Mass left after 25 days = ?
Solution:
First of all we will calculate the number of half lives passes in given time period.
Number of half lives = Time elapsed / Half life
Number of half lives = 25 days/ 5 days
Number of half lives = 5
At time zero = 400 g
At 1st half life = 400 g/2 = 200 g
At 2nd half life = 200 g/2 = 100 g
At 3rd half life = 100 g/2 = 50 g
At 4th half life = 50 g/2 = 25 g
At 5th half life = 25 g/2 = 12.5 g
(a) Matter cannot be created and destroyed by a chemical reaction.
Explanation:
(a) Matter cannot be created and destroyed by a chemical reaction. (correct)
The number and type of atoms entering the chemical reaction are the same with the number and type of atoms leaving the chemical reaction.
(b) The reactants are the same substance as the products. (wrong)
You may see in the reaction that we have as reactants zinc and hydrochloric acid which react to form the products, zinc chloride and hydrogen.
(c) The number of molecules in the reactants are equal to the number of molecules in the products. (wrong)
As reactants we have 2 hydrochloric acid (HCl) molecules and as products 1 hydrogen (H₂) molecule. Zn is a metal and ZnCl is a salt.
(d) The atoms on the reactants side are changed into different atoms on the products side. (wrong)
The number and type of atoms entering the chemical reaction are the same with the number and type of atoms leaving the chemical reaction.
Learn more about:
balancing chemical equations
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