HSC_Chem_Past_Paper_Sol

# Plotted correctlysup1sup axes labelled with

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Unformatted text preview: L) (at 25°C & 100kPa) curve of best fit 200 outlier ignored in curve of best fit 100 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 mass zinc (g) To recieve 2/3 marks. *Points plotted correctly<sup>1</sup> *Axes labelled with units<sup>1</sup> *Linear scale used on axes<sup>1</sup> To recieve 3/3 marks: *Outlier plotted but not included in graph (line of best fit)<sup>1</sup> (but the question never asks for a line of best fit) *Intersection point indicated<sup>1</sup> *Lines connecting data points are straight<sup>1</sup> (but question never asks for linear interpolation of data???) *Points plotted correctly<sup>1</sup> _____________________________________________________________________________________________________ HSC CHEMISTRY PAST PAPER SOLUTIONS – ANDREW HARVEY 10 2.0 2000 HSC ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– *Axes labelled<sup>1</sup> *Linear scales used on axes<sup>1</sup> :"Better responses identified the independent and dependent variables and labelled the axes correctly. They ensured that axes had linear scales that used the extent of the grid provided. Most candidates plotted the points correctly by marking the point with a cross or a circle. The better candidates used a pencil and ruler to draw two lines of best fit that intersected at a point and left out the outlier point from the line of best fit."<sup>1</sup> (b) 380mL. Once the volume of gass produced reaches 380mL all the H<sub>2<sub> has been used up. HCl is the limiting reagent. So no matter how much more zinc there is, there is not enough HCl for the reaction to occur. :"Most candidates identified the correct volume; however, many did not use the correct unit for volume, milliliter (mL), although it was indicated in the table. The better responses identified that hydrochloric acid (HCl) was the limiting reagent."<sup>1</sup> (c) 106.15 mL Question 23: (a) Incomplete combustion results when there is a lack of oxygen.<sup>1</sup> (b) $3CH_{4 \left ( g \right )} + \frac {9}{2} O_{2 \left ( g \right )} \rightarrow C_{\left ( s \right )} + CO_{\left ( g \right )} + CO_{2 \left ( g \right )} + 6H_2O_{\left ( l \right )}$ Question 24: (a) $CaCO_{3 \left ( s \right )} + 2HCl_{\left ( l \right )} \rightarrow CaCl_{2 \left ( aq \right )} + H_2O_{\left ( l \right )} + CO_{2 \left ( g \right )}$ (b) $c = \frac {n}{v}$ $0.6 = \frac {n}{25 \times 10^{-3}}$ $n = 0.6 \times 25 \times 10^{-3} = 0.015$ moles (c) 0.6796 g Question 25: (a) This question is asking for the percentage of tot...
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## This document was uploaded on 09/19/2013.

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