You must know and use the formula for pH.
pH = - log [H3O+], where [H3O+] is the molar concentration of hydronium ion.
So, when pH is 8.0 => 8.0 = - log [H3O+] and you can use antilogarithm (the inverse function of logarithm) to find [H3O+], in this way:
[H3O+] = 10^-8 = 1 * 10 ^-8 M
When, pH = 7.0 =>
7.0 = - log [H3O+] => [H3O+] = 1 * 10^ -7 M
Answer: 1*10^-7 mole / liter
Period are going left to right across the periodic table
Groups are going up to down on the periodic table
The density of water is 1.0 grams per milliliter then it will be sink in water
Density is a word we use to describe how much space an object or substance takes up in the volume and in relation to the amount of matter in that object or substance its mass) and another way to put it is that density is the amount of mass per unit of volume
Here given density is 1.0 grams per milliliter and it will be sink in water because the density of water in 1.0 g/ml and this object is more dense than water and the density of an object determines whether it will float or sink in another substance and an object will float if it is less dense than the liquid it is placed in and an object will sink if it is more dense than the liquid it is placed
Know more about density
brainly.com/question/18366165
#SPJ1