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)
Given:

Putting values in equation 1, we get:

Hence, the momentum of the child and milk together is 58.125 kg.m/s
Copper (II) Carbonate + Heat yields copper (II) oxide and carbon dioxide
Molecular Equation: CuCo3 + heat > CuO + CO2
You need to look at the electronegativity and decide wheter the difference of both of the numbers are significant enough to form a polar bond
The use of cold methanol is important because it is used to recrystallize or solidify the product.
Since, ice bath is also used in nitration of methyl benzoate because in this reaction the concentrated acid like sulfuric acid is used with water and it is very exothermic.
The formation pure solid from the impure solid compound by mixing with hot solvent and form saturated solution. Now, this solution as cools and pure crystal grows when solubility of the compound decreases. This whole process is called re-crystallization.
learn about re-crystallization
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