Answer:
 [H⁺] =  3.16 × 10⁻⁵ mol/L
Explanation:
Given data:
pH of solution = 4.5
Hydrogen ion concentration = ?
Solution;
pH = -log [H⁺]
we will rearrange this formula:
 [H⁺] =  10∧-pH
 [H⁺] = 10⁻⁴°⁵
 [H⁺] =  3.16 × 10⁻⁵ mol/L
 
        
             
        
        
        
Compound can be described using element symbol and numbers .  it is a mixture which is result of two or more chemical element in such a way that atoms of different elements held together  by chemical compound that are difficult to break . Most often a compound looks and behave like an element 
 for example :-   Hydrogen   and oxygen ..   both of these elements are gaseous at room temperature and atmospheric pressure , but when both combined they both form compound water . ( H2O )
        
             
        
        
        
It will take 15 s to travel 6 cm
<h3>Further explanation</h3>
Given
distance versus time graph
Required
time travel
Solution
Caterpillar motion is a straight motion with a constant speed, so that the graph between distance and time forms a diagonal line
If we look at the graph, we can determine the time taken when the distance reaches 6 cm (y axis) by drawing a line to the diagonal line and cutting the x-axis as time, and we get 15 s
Or we can also use the formula for motion at constant speed:
d = v x t
With v at point 2,5 of 2/5 m / s, so the time taken:
