The question is incomplete. The complete question is :
A 100.0 mL flask is filled with 0.065 moles of A and allowed to react to form B according to the reaction below. The following experimental data are obtained for the amount of A as the reaction proceeds. What is the average rate of appearance of B in units of M/s between t = 10 min. and t = 30 min.? Assume that the volume of the flask is constant. A(g) → B(g)
Time 0.0 10.0 20.0 30.0 40.0
Moles of A 0.065 0.051 0.042 0.036 0.031
Solution :
Consider the following reaction as follows :

The experiment data is given as follows :
Time (min) : 0.0 10.0 20.0 30.0 40.0
Moles of A : 0.065 0.051 0.042 0.036 0.031
According to the rate of reaction concept, the rate can be expressed as a consumption of the reactant and formation of the product as follows :
Average rate : ![$= -\frac{d[A]}{dt} = \frac{d[B]}{dt} $](https://tex.z-dn.net/?f=%24%3D%20-%5Cfrac%7Bd%5BA%5D%7D%7Bdt%7D%20%3D%20%20%5Cfrac%7Bd%5BB%5D%7D%7Bdt%7D%20%24)
Now we have to calculate the average rate between 10.0 to 30.0 min w.r.t. A as follows :
Rate 


Therefore, the rate = 
Answer: here is your answer
Explanation:
The oxygen family consists of the elements that make up group 16 on the periodic table: oxygen, sulfur, selenium, tellurium, and polonium. These elements all have six electrons in their outermost energy level, accounting for some common chemical properties among them.
This sounds like paper chromatography. Let me know in the comments if the answer is something else.
Answer:
2.70 M.
Explanation:
Molar mass of MgO = 24.3 + 16 = 40.3.
A molar solution will contain 40.3g in 1 Litre.
So 800 mL of 1 molar solution will contain 0.8* 40.3 g MgO.
So the molarity of the given solution
= 87 / (0.8*40.3)
= 2.699 M.