<u>Answer:</u> The density of NaCl solution is 3.930 g/mL
<u>Explanation:</u>
We are given:
Mass of cylinder,  = 21.577 g
 = 21.577 g
Mass of NaCl and cylinder combined, M = 39.664 g
Mass of NaCl,  =
 = 
To calculate density of a substance, we use the equation:

We are given:
Mass of NaCl = 18.087 g
Volume of NaCl solution = 4.602 mL
Putting values in above equation, we get:

Hence, the density of NaCl solution is 3.930 g/mL
 
        
             
        
        
        
Answer:
When the electron changes levels, it decreases energy and the atom emits photons. The photon is emitted with the electron moving from a higher energy level to a lower energy level. The energy of the photon is the exact energy that is lost by the electron moving to its lower energy level.
Explanation:
 
        
                    
             
        
        
        
I disagree with the answer pick of D. If you have a neutral pH 7 solution and you proceed to add a base even with an relatively insignificantly low Kb your solution would still be more basic then acidic. The answer should be b which is true that the base only ionizes slightly in aqueous solution. This is also truer to the definition of what Kb represents.
        
             
        
        
        
Answer: The momentum of the child and milk together is 58.125 kg.m/s
Explanation:
Momentum is defined as the product of object's mass and velocity.
Mathematically,

where, p = momentum
m = mass of the object
v = velocity of the object
In the given question, we are given that a child of mass 21.0 kg is carrying a gallon of milk having mass 2.25 kg and running with a velocity of 2.5 m/s. Hence, the momentum by both milk and child will be:
 ....(1)
      ....(1)
Given:

Putting values in equation 1, we get:

Hence, the momentum of the child and milk together is 58.125 kg.m/s