Hi mate. I think the answer is 100
Answer: The rate of appearance of
is 
Explanation:
Rate law says that rate of a reaction is directly proportional to the concentration of the reactants each raised to a stoichiometric coefficient determined experimentally called as order.

The rate in terms of reactants is given as negative as the concentration of reactants is decreasing with time whereas the rate in terms of products is given as positive as the concentration of products is increasing with time.
Rate in terms of disappearance of HBr =
= ![\frac{1d[H_2]}{dt}](https://tex.z-dn.net/?f=%5Cfrac%7B1d%5BH_2%5D%7D%7Bdt%7D)
Rate in terms of appearance of
= ![\frac{1d[Br_2]}{dt}](https://tex.z-dn.net/?f=%5Cfrac%7B1d%5BBr_2%5D%7D%7Bdt%7D)
![-\frac{1d[HBr]}{2dt}=\frac{d[H_2]}{dt}=\frac{d[Br_2]}{dt}](https://tex.z-dn.net/?f=-%5Cfrac%7B1d%5BHBr%5D%7D%7B2dt%7D%3D%5Cfrac%7Bd%5BH_2%5D%7D%7Bdt%7D%3D%5Cfrac%7Bd%5BBr_2%5D%7D%7Bdt%7D)
Given :
![-\frac{1d[HBr]}{dt}=0.140Ms^{-1}](https://tex.z-dn.net/?f=-%5Cfrac%7B1d%5BHBr%5D%7D%7Bdt%7D%3D0.140Ms%5E%7B-1%7D)
The rate of appearance of
;
![\frac{1d[Br_2]}{dt}=-\frac{1d[HBr]}{2dt}=\frac{1}{2}\times 0.140=0.0700Ms^{-1}](https://tex.z-dn.net/?f=%5Cfrac%7B1d%5BBr_2%5D%7D%7Bdt%7D%3D-%5Cfrac%7B1d%5BHBr%5D%7D%7B2dt%7D%3D%5Cfrac%7B1%7D%7B2%7D%5Ctimes%200.140%3D0.0700Ms%5E%7B-1%7D)
Thus rate of appearance of
is 
274ml's that is if you are converting from Liters
Answer:
Mass 1=3M
Mass 2=?
Volume1=75mL
Volume2=250mL
By using molarity formula:
<u>mass1*volume 1=mass2*volume 2</u>
3M*75=mass2*250
mass2=225/250
mass2:0.9M
<h3>the molarity of a solution is 0.9M.</h3>