Answer:
0.257 L
Explanation:
The values missing in the question has been assumed with common sense so that the concept could be applied
Initial volume of the AICI3 solution
Initial Molarity of the solution
Final molarity of the solution
Final volume of the solution
From Law of Dilution,
Final Volume of the solution 
Answer:
b) 
The confidence interval for this case is given (6.21, 6.59)
So we can conclude at 95% of confidence that the true mean for the PH concentration is between 6.21 and 6.59 moles per liter
c) Since the confidence interval not contains the value 7 we reject the hypothesis that the true mean is equal to 7. And the same result was obtained with the t test for the true mean.
Explanation:
We assume that part a is test the claim. And we can conduct the following hypothesis test:
Null hypothesis: 
Alternative hypothesis 
The statistic is to check this hypothesi is given by:

We know the following info from the problem:

Replacing we got:

And the p value would be:

Since the p value is very low compared to the significance assumed of 0.05 we have enough evidence to reject the null hypothesis that the true mean is equal to 7 moles/liter
Part b
The confidence interval is given by:

The confidence interval for this case is given (6.21, 6.59)
So we can conclude at 95% of confidence that the true mean for the PH concentration is between 6.21 and 6.59 moles per liter
Part c
Since the confidence interval not contains the value 7 we reject the hypothesis that the true mean is equal to 7. And the same result was obtained with the t test for the true mean.