Answer: B- a roll of photographic film
Explanation:
Founders education answer
Mass number = protons + neutrons. 12 + 11 = 23.
Answer : Option D) The pH of the solution is 8.0.
Explanation : pOH of a solution is a measure of hydroxide ion 
concentration in a particular solution. It gives the measure of alkalinity of a solution. Normally, aqueous solutions at 25°C have pOH which is less than 7 are usually alkaline, when pOH is found to be greater than 7 then they are acidic and when pOH will be equal to 7 then it is neutral.
pH + pOH = 14, this relationship is used to find pH of any unknown solution with given pOH value,
Here, we known pOH is 6.0, so we get,
pH = 14 - 6 = 8.0;
Hence, the pH will be 8.0.
Use the 1st order decay equation
<span><span>Cfinal</span>=<span>Cinitial</span><span>e<span>−kt</span></span></span>
by filling in and doing the math you will get:
<span> </span><span>Cfinal</span><span> = 1.11 grams Rn-222 after 23 days.
hope this helps
</span>
M = n x Mr
Mr of H20 - 18.006
M = 1.15mol x 18.006g/mol
= 20.7069g
= 20.7g (3sfg)
