Synthesise the CBZ derivative of glycine from glycine and benzyl chloroformate Question
  The benzyloxycarbonyl group (CBZ) is widely used to protect amines, especially in aminoacid chemistry. A procedure to synthesise the CBZ derivative of glycine from glycine and benzyl chloroformate is given in the description below. 
  
  Glycine ($0.1~\mathrm{mol}$) was dissolved in aqueous sodium hydroxide ($50~\mathrm{mL}$ of a $2~\mathrm{M}$ solution) 
  and the solution was cooled in an ice bath. Benzyl chloroformate ($1.2~
\mathrm{eq}$) and aqueous 
  sodium hydroxide ($25~\mathrm{mL}$ of a $4~\mathrm{M}$ solution) were added dropwise simultaneously to the 
  glycine solution at $0°\mathrm{C}$ dropwise over thirty minutes. The mixture was stirred for an extra 
  ten minutes, then warmed to room temperature. The solution was extracted twice with 
  ether. The combined organic layers were acidified to $\mathrm{pH}=1$. The precipitate was filtered, 
  washed with a little cold water and dried to give carbobenzoxyglycine ($18.5~\mathrm{g}$), m.p. $119-120°\mathrm{C}$.
  
  (a) Relative to glycine, how many equivalents of sodium hydroxide are used in this reaction? Explain why this number was used.
  
  (b) Can sodium carbonate ($\ce{Na2CO3}$) be used in place 
  of sodium hydroxide? Explain why it can or cannot be used.
  
  (c) What inorganic by-product will be formed (write its chemical name)?
  
  (d) The procedure given includes a serious mistake, which would result in a yield of $0\%$. 
  What is the mistake, and how might it be corrected?


My answers

(a) I mentioned $1~\mathrm{eq}$ of sodium hydroxide as sodium hydroxide reacts with glycine in a 1:1 ratio.

(b) I mentioned that sodium carbonate cannot be used in place of sodium hydroxide as sodium Carbonate is not basic enough to catalyst the reaction.

(c) Sodium chloride 

(d) I mentioned that during the process when the combined organic layers were acidified to $\mathrm{pH}=1$, it could destroy the product by hydrolysing it hence giving a yield of $0\%$.

I'm unsure whether my answers are correct though, could anyone explain? Also, are there any resources on the web that contain practice questions of a similar nature to this?
I agree with Ron's answer except for d. Using an extra equivalent of NaOH is the right procedure since you need to "mop up" the HCl that is produced when $\ce{CbzCl}$ reacts with the amino group. What is not correct is this:
When you wash the reaction mixture with ether you get rid of any impurities and your product should stay in the aqueous phase. So you have to acidify the aqueous layer and not the ether one. pH 1 should be fine for the Cbz unless you leave it there and go away for the weekend.