Calculate the mass of solid sodium hydrogen carbonate required to make 250 mL of 0.12 mol L\(^{-1}\) solution. (2 marks)
CHEMISTRY, M2 2006 HSC 18
A student studying the mass change that occurs during fermentation added glucose, water and yeast to a flask and stoppered the flask with some cotton wool.
The student measured the mass of the flask daily for seven days. The table shows the data collected.
\begin{array} {|c|c|}
\hline
\rule{0pt}{2.5ex}\ \ \ \textit{Day}\ \ \ \rule[-1ex]{0pt}{0pt} & \ \ \textit{Mass}\ \text{(g)}\ \ \\
\hline
\rule{0pt}{2.5ex} 1 \rule[-1ex]{0pt}{0pt} & 381.05\\
\hline
\rule{0pt}{2.5ex} 2 \rule[-1ex]{0pt}{0pt} & 376.96\\
\hline
\rule{0pt}{2.5ex} 3 \rule[-1ex]{0pt}{0pt} & 373.42\\
\hline
\rule{0pt}{2.5ex} 4 \rule[-1ex]{0pt}{0pt} & 370.44\\
\hline
\rule{0pt}{2.5ex} 5 \rule[-1ex]{0pt}{0pt} & 370.42\\
\hline
\rule{0pt}{2.5ex} 6 \rule[-1ex]{0pt}{0pt} & 370.40\\
\hline
\rule{0pt}{2.5ex} 7 \rule[-1ex]{0pt}{0pt} & 370.39\\
\hline
\end{array}
- Calculate the moles of \(\ce{CO2}\) released between days 1 and 7. (1 mark)
--- 2 WORK AREA LINES (style=lined) ---
- Calculate the mass of glucose that underwent fermentation between days 1 and 7. Include a balanced chemical equation in your answer. (3 marks)
--- 6 WORK AREA LINES (style=lined) ---
CHEMISTRY, M2 2009 HSC 22
The nitrogen content of bread was determined using the following procedure:
-
- A sample of bread weighing 2.80 g was analysed.
- The nitrogen in the sample was converted into ammonia.
- The ammonia was collected in 50.0 mL of 0.125 mol L\(^{-1}\) hydrochloric acid. All of the ammonia was neutralised, leaving an excess of hydrochloric acid.
- The excess hydrochloric acid was titrated with 23.30 mL of 0.116 mol L\(^{-1}\) sodium hydroxide solution.
- Write balanced equations for the TWO reactions involving hydrochloric acid. (2 marks)
--- 4 WORK AREA LINES (style=lined) ---
- Calculate the moles of excess hydrochloric acid. (1 mark)
--- 2 WORK AREA LINES (style=lined) ---
- Calculate the moles of ammonia. (2 marks)
--- 4 WORK AREA LINES (style=lined) ---
- Calculate the percentage by mass of nitrogen in the bread. (2 marks)
--- 4 WORK AREA LINES (style=lined) ---