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1194 lines (1176 loc) · 39.3 KB
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>CHEMICAL ENERGETICS</title>
<script src="mcq2.js" defer></script>
<meta name="keywords" content="kemguru, objective questions">
<meta name="author" content="Jiban Majumdar">
<meta name="acknowledgement-UCLES" content="multiple-choice questions of IGCSE past papers">
<link rel="stylesheet" href="mystyle.css">
</head>
<body>
<a href="index.html" target="_top">
<h4>"kemguru" home page</h4>
</a>
<div>
<img src="myPhoto.jpg" alt="webmaster" width="150" height="200"> <br>
<a href="mailto:jibanmajumdar@gmail.com">webmaster</a>
</div>
<p></p>
<h1 style="text-align:center;">CHEMICAL ENERGETICS</h1>
<p></p><h2 style="text-align:left;">Direction:</h2> <h3>For each question
there are four possible answers A,B,C and D. Choose the one you consider correct , click the radio button next to it and then click the button "Check Answer ".</h3>
<p></p>
1. The reaction pathway diagram for a reaction is shown.<p></p>
<img src="pic127.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
Which statements are correct?<p></p>
i. The reaction is exothermic.<br>
ii. The reaction is endothermic.<br>
iii. The temperature of the surroundings increases.<br>
iv. The temperature of the surroundings decreases.<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'D');">
<input type="radio" value="A" name="mc">
A. i and iii<br>
<input type="radio" value="B" name="mc">
B. i and iv<br>
<input type="radio" value="C" name="mc">
C. ii and iii<br>
<input type="radio" value="D" name="mc">
D. ii and iv<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
2. A reaction pathway diagram is shown.<p></p>
<img src="pic136.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
Which statement about this reaction is correct?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. The reaction rate increases during the reaction.<br>
<input type="radio" value="B" name="mc">
B. The reaction is endothermic.<br>
<input type="radio" value="C" name="mc">
C. The reaction transfers thermal energy to the surroundings.<br>
<input type="radio" value="D" name="mc">
D. The temperature of the surroundings increases.<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
3. The initial and final temperatures of four different reactions are measured.<br>
Which reaction is the least exothermic?<br>
<table class="center">
<tr>
<th> </th>
<th>Initial temperature / <sup>o</sup>C</th>
<th>Final temperature / <sup>o</sup>C</th>
</tr>
<tr>
<td>A</td>
<td>19</td>
<td>25</td>
</tr>
<tr>
<td>B</td>
<td>21</td>
<td>18</td>
</tr>
<tr>
<td>C</td>
<td>22</td>
<td>17</td>
</tr>
<tr>
<td>D</td>
<td>22</td>
<td>26</td>
</tr>
</table>
<form method="post"
onSubmit="return checkAnswer(this,'D');">
<input type="radio" value="A" name="mc">
A. <br>
<input type="radio" value="B" name="mc">
B. <br>
<input type="radio" value="C" name="mc">
C. <br>
<input type="radio" value="D" name="mc">
D. <br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
4. The equation for the combustion of methane is shown: CH<sub>4</sub> + 2O<sub>2</sub> → CO<sub>2</sub> + 2H<sub>2</sub>O<p></p>
The energy change for the combustion of methane is –890 kJ / mol.<p></p>
The bond energies are shown in the table.
<table class="center">
<tr>
<th>bond</th>
<th>bond energy in kJ / mol</th>
</tr>
<tr>
<td>C–H</td>
<td>+410</td>
</tr>
<tr>
<td>O=O</td>
<td>496</td>
</tr>
<tr>
<td>H–O</td>
<td>460</td>
</tr>
</table><p></p>
What is the bond energy of the C=O bond?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. +49 kJ / mol<br>
<input type="radio" value="B" name="mc">
B. +841 kJ / mol <br>
<input type="radio" value="C" name="mc">
C. +1301 kJ / mol<br>
<input type="radio" value="D" name="mc">
D. +1335 kJ / mol<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
5. Hydrogen burns in oxygen.<br>
The equation for the reaction is shown: 2H<sub>2</sub> + O<sub>2</sub>→ 2H<sub>2</sub>O<br>
The table shows the bond energies involved.<p></p>
<table class="center">
<tr>
<th>bond</th>
<th>bond energy in kJ / mol</th>
</tr>
<tr>
<td>H–H</td>
<td>436</td>
</tr>
<tr>
<td>O=O</td>
<td>498</td>
</tr>
<tr>
<td>O–H</td>
<td>464</td>
</tr>
</table><p></p>
What is the energy given out during the reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'C');">
<input type="radio" value="A" name="mc">
A. –3226 kJ / mol<br>
<input type="radio" value="B" name="mc">
B. –884 kJ / mol <br>
<input type="radio" value="C" name="mc">
C. –486 kJ / mol<br>
<input type="radio" value="D" name="mc">
D. –442 kJ / mol<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
6. Which equation represents an endothermic reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'A');">
<input type="radio" value="A" name="mc">
A. Cl<sub>2</sub>(g) →2Cl (g)<br>
<input type="radio" value="B" name="mc">
B. CH<sub>4</sub>(g) + 2O<sub>2</sub>(g) → CO<sub>2</sub>(g) + 2H<sub>2</sub>O(l) <br>
<input type="radio" value="C" name="mc">
C. H(g) + H(g) → H<sub>2</sub>(g)<br>
<input type="radio" value="D" name="mc">
D. 2K(s) + 2H<sub>2</sub>O(l) → 2KOH(aq) + H<sub>2</sub>(g)<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
7. Methane burns in oxygen to form carbon dioxide and water: CH<sub>4</sub>(g) + 2O<sub>2</sub>(g) → CO<sub>2</sub>(g) + 2H<sub>2</sub>O(l)<br>
The bond energies are shown.<p></p>
<table class="center">
<tr>
<th>bond</th>
<th>bond energy
in kJ / mol</th>
</tr>
<tr>
<td>C–H</td>
<td>410</td>
</tr>
<tr>
<td>C–O</td>
<td>360</td>
</tr>
<tr>
<td>C=O</td>
<td>805</td>
</tr>
<tr>
<td>O–H</td>
<td>460</td>
</tr>
<tr>
<td>O–O</td>
<td>146</td>
</tr>
<tr>
<td>O=O</td>
<td>496</td>
</tr>
</table><p></p>
What is the energy change for this reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'A');">
<input type="radio" value="A" name="mc">
A. –818 kJ / mol<br>
<input type="radio" value="B" name="mc">
B. –102 kJ / mol <br>
<input type="radio" value="C" name="mc">
C. +102 kJ / mol<br>
<input type="radio" value="D" name="mc">
D. +818 kJ / mol<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
8. Ethene reacts with hydrogen. The equation is shown: C<sub>2</sub>H<sub>4</sub> + H<sub>2</sub> → C<sub>2</sub>H<sub>6</sub><br>
The bond energies are shown.<p></p>
<table class="center">
<tr>
<th>bond</th>
<th>bond energy
in kJ / mol</th>
</tr>
<tr>
<td>C–C</td>
<td>+350</td>
</tr>
<tr>
<td>C=C</td>
<td>+610</td>
</tr>
<tr>
<td>C–H</td>
<td>+410</td>
</tr>
<tr>
<td>H–H</td>
<td>+436</td>
</tr>
</table><p></p>
What is the energy change for this reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. –560 kJ / mol<br>
<input type="radio" value="B" name="mc">
B. –124 kJ / mol <br>
<input type="radio" value="C" name="mc">
C. +486 kJ / mol<br>
<input type="radio" value="D" name="mc">
D. +5496 kJ / mol<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
9. When an acid is added to an alkali, the temperature of the reaction mixture rises.<br>
Which words describe this reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'D');">
<input type="radio" value="A" name="mc">
A. Decomposition and endothermic.<br>
<input type="radio" value="B" name="mc">
B. Decomposition and exothermic. <br>
<input type="radio" value="C" name="mc">
C. Neutralisation and endothermic.<br>
<input type="radio" value="D" name="mc">
D. Neutralisation and exothermic.<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
10. The temperature decreases when aqueous ethanoic acid reacts with solid sodium carbonate to
form a salt.<br>
Which type of reaction and energy change occur?<p></p>
<table class="center">
<tr>
<th></th>
<th>type of reaction</th>
<th>energy change</th>
</tr>
<tr>
<td>A</td>
<td>neutralisation</td>
<td>endothermic</td>
</tr>
<tr>
<td>B</td>
<td>neutralisation</td>
<td>exothermic</td>
</tr>
<tr>
<td>C</td>
<td>redox</td>
<td>endothermic</td>
</tr>
<tr>
<td>D</td>
<td>redox</td>
<td>exothermic</td>
</tr>
</table><p></p>
<form method="post"
onSubmit="return checkAnswer(this,'A');">
<input type="radio" value="A" name="mc">
A. <br>
<input type="radio" value="B" name="mc">
B. <br>
<input type="radio" value="C" name="mc">
C. <br>
<input type="radio" value="D" name="mc">
D. <br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
11. An energy level diagram for a reaction is shown.<p></p>
<img src="pic131.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
Which statement and explanation about this reaction are correct?<p></p>
<table class="center">
<tr>
<th> </th>
<th>statement</th>
<th>explanation</th>
</tr>
<tr>
<td>A</td>
<td>the reaction is endothermic</td>
<td>the products have more energy than the reactants</td>
</tr>
<tr>
<td>B</td>
<td>the reaction is endothermic</td>
<td>the products have less energy than the reactants</td>
</tr>
<tr>
<td>C</td>
<td>the reaction is exothermic</td>
<td>the products have more energy than the reactants</td>
</tr>
<tr>
<td>D</td>
<td>the reaction is exothermic</td>
<td>the products have less energy than the reactants</td>
</tr>
</table>
<form method="post"
onSubmit="return checkAnswer(this,'D');">
<input type="radio" value="A" name="mc">
A. <br>
<input type="radio" value="B" name="mc">
B. <br>
<input type="radio" value="C" name="mc">
C. <br>
<input type="radio" value="D" name="mc">
D. <br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
12. The energy level diagram for a chemical reaction is shown.<p></p>
<img src="pic129.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
Which statement about this reaction is correct?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. The reaction is endothermic and energy is given out to the surroundings.<br>
<input type="radio" value="B" name="mc">
B. The reaction is endothermic and energy is taken in from the surroundings.<br>
<input type="radio" value="C" name="mc">
C. The reaction is exothermic and energy is given out to the surroundings.<br>
<input type="radio" value="D" name="mc">
D. The reaction is exothermic and energy is taken in from the surroundings.<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
13. Chlorine reacts with ethane to produce chloroethane and hydrogen chloride.<p></p>
<img src="pic130.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
The bond energies are shown in the table.<p></p>
<table class="center">
<tr>
<th>bond</th>
<th>bond energy
in kJ / mol</th>
</tr>
<tr>
<td>C–Cl</td>
<td>+340</td>
</tr>
<tr>
<td>C–C</td>
<td>+350</td>
</tr>
<tr>
<td>C–H</td>
<td>+410</td>
</tr>
<tr>
<td>Cl–Cl</td>
<td>+240</td>
</tr>
<tr>
<td>H–Cl</td>
<td>+430</td>
</tr>
</table><p></p>
What is the energy change for this reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. –1420 kJ / mol<br>
<input type="radio" value="B" name="mc">
B. –120 kJ / mol <br>
<input type="radio" value="C" name="mc">
C. +120 kJ / mol<br>
<input type="radio" value="D" name="mc">
D. +1420 kJ / mol<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
14. Sodium nitrate is added to water in a beaker and stirred until it dissolves.<br>
At the end of the experiment, the beaker feels cold.<p></p>
Which row describes the reaction?<p></p>
<table class="center">
<tr>
<th> </th>
<th>Temperature of solution/th>
<th>Type of reaction</th>
</tr>
<tr>
<td>A</td>
<td>Decreases</td>
<td>Endothermic</td>
</tr>
<tr>
<td>B</td>
<td>Decreases</td>
<td>Exothermic</td>
</tr>
<tr>
<td>C</td>
<td>Increases</td>
<td>Endothermic</td>
</tr>
<tr>
<td>D</td>
<td>Increases</td>
<td>Exothermic</td>
</tr>
</table>
<form method="post"
onSubmit="return checkAnswer(this,'A');">
<input type="radio" value="A" name="mc">
A. <br>
<input type="radio" value="B" name="mc">
B. <br>
<input type="radio" value="C" name="mc">
C. <br>
<input type="radio" value="D" name="mc">
D. <br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
15. Which substance does not require oxygen in order to produce energy?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'D');">
<input type="radio" value="A" name="mc">
A. Coal.<br>
<input type="radio" value="B" name="mc">
B. hydrogen.<br>
<input type="radio" value="C" name="mc">
C. Natural gas<br>
<input type="radio" value="D" name="mc">
D. <sup>235</sup>U<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
16. Which statements about endothermic reactions are correct?<p></p>
i. The energy of the products is greater than the energy of the reactants.<br>
ii. The energy of the reactants is greater than the energy of the products.<br>
iii.The temperature of the surroundings increases during the reaction.<br>
iv. The temperature of the surroundings decreases during the reaction.<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. i and iii only.<br>
<input type="radio" value="B" name="mc">
B. i and iv only.<br>
<input type="radio" value="C" name="mc">
C. ii and iii only.<br>
<input type="radio" value="D" name="mc">
D. ii and iv only.<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
17. The temperature of the water in two beakers, X and Y, is measured as 21.5 °C.<br>
5 g of sodium chloride is dissolved in the water in beaker X. The temperature changes to 18.0 °C.<br>
5 g of calcium oxide is dissolved in the water in beaker Y. The temperature changes to 29.4 °C.<p></p>
Which types of process are occurring in beakers X and Y?<p></p>
<table class="center">
<tr>
<th> </th>
<th>X</th>
<th>Y</th>
</tr>
<tr>
<td>A</td>
<td>Endothermic</td>
<td>Endothermic</td>
</tr>
<tr>
<td>B</td>
<td>Endothermic</td>
<td>Exothermic</td>
</tr>
<tr>
<td>C</td>
<td>Exothermic</td>
<td>Endothermic</td>
</tr>
<tr>
<td>D</td>
<td>Exothermic</td>
<td>Exothermic</td>
</tr>
</table>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. <br>
<input type="radio" value="B" name="mc">
B. <br>
<input type="radio" value="C" name="mc">
C. <br>
<input type="radio" value="D" name="mc">
D. <br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
18. An energy level diagram for the reaction between substance X and substance Y to form
substance Z is shown.<p></p>
<img src="pic128.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
Which statement is correct?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. Energy is released as substance Z is formed.<br>
<input type="radio" value="B" name="mc">
B. Substance Z has more energy than substance X and substance Y.<br>
<input type="radio" value="C" name="mc">
C. The reaction is exothermic.<br>
<input type="radio" value="D" name="mc">
D. When substance X and substance Y react, the temperature increases.<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
19. Which changes occur when hydrogen is burned in oxygen?<p></p>
<table class="center">
<tr>
<th> </th>
<th>energy change</th>
<th>product</th>
</tr>
<tr>
<td>A</td>
<td>Endothermic</td>
<td>H<sub>2</sub>O only</td>
</tr>
<tr>
<td>B</td>
<td>Endothermic</td>
<td>H<sub>2</sub>O and CO<sub>2</sub></td>
</tr>
<tr>
<td>C</td>
<td>Exothermic</td>
<td>H<sub>2</sub>O only</td>
</tr>
<tr>
<td>D</td>
<td>Exothermic</td>
<td>H<sub>2</sub>O and CO<sub>2</sub></td>
</tr>
</table>
<form method="post"
onSubmit="return checkAnswer(this,'C');">
<input type="radio" value="A" name="mc">
A. <br>
<input type="radio" value="B" name="mc">
B. <br>
<input type="radio" value="C" name="mc">
C. <br>
<input type="radio" value="D" name="mc">
D. <br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
20. The equation for the formation of ammonia is shown: N<sub>2</sub> + 3H<sub>2</sub> → 2NH<sub>3</sub><br>
The energy level diagram for the reaction is shown.<p></p>
<img src="pic132.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
What is the energy change for the reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. –592 kJ / mol<br>
<input type="radio" value="B" name="mc">
B. –92 kJ / mol<br>
<input type="radio" value="C" name="mc">
C. +92 kJ / mol<br>
<input type="radio" value="D" name="mc">
D. +592 kJ / mol<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
21. Ethene burns in oxygen to form carbon dioxide and water vapour.<p></p>
<img src="pic133.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
The bond energies are shown in the table.<p></p>
<table class="center">
<tr>
<th>bond</th>
<th>bond energy
in kJ / mol</th>
</tr>
<tr>
<td>C=C</td>
<td>+610</td>
</tr>
<tr>
<td>C–H</td>
<td>+410</td>
</tr>
<tr>
<td>O=O</td>
<td>+497</td>
</tr>
<tr>
<td>C=O</td>
<td>+805</td>
</tr>
<tr>
<td>O–H</td>
<td>+460</td>
</tr>
</table><p></p>
What is the energy change for this reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'C');">
<input type="radio" value="A" name="mc">
A. –2959 kJ / mol<br>
<input type="radio" value="B" name="mc">
B. –2313 kJ / mol <br>
<input type="radio" value="C" name="mc">
C. –1319 kJ / mol<br>
<input type="radio" value="D" name="mc">
D. –399 kJ / mol<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
22. When dilute sulfuric acid reacts with aqueous sodium hydroxide, the temperature of the solution
increases.<p></p>
Which words describe this reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'C');">
<input type="radio" value="A" name="mc">
A. endothermic and neutralisation<br>
<input type="radio" value="B" name="mc">
B. endothermic and redox<br>
<input type="radio" value="C" name="mc">
C. exothermic and neutralisation<br>
<input type="radio" value="D" name="mc">
D. exothermic and redox<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
23. Water is added to anhydrous copper(II) sulfate in a test-tube. The mixture becomes hot.<p></p>
Which type of reaction and energy level diagram apply to this reaction?<p></p>
<img src="pic134.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
<form method="post"
onSubmit="return checkAnswer(this,'C');">
<input type="radio" value="A" name="mc">
A. <br>
<input type="radio" value="B" name="mc">
B. <br>
<input type="radio" value="C" name="mc">
C. <br>
<input type="radio" value="D" name="mc">
D. <br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
24. Which reaction is endothermic?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'D');">
<input type="radio" value="A" name="mc">
A. neutralisation of an acid by an alkali<br>
<input type="radio" value="B" name="mc">
B. reaction of hydrogen with oxygen<br>
<input type="radio" value="C" name="mc">
C. reaction of sodium with water<br>
<input type="radio" value="D" name="mc">
D. thermal decomposition of limestone<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
25. The compound hydrazine is used as a rocket fuel. It has the structural formula shown:<p></p>
<img src="pic135.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
One of the reactions of hydrazine is shown: N<sub>2</sub>H<sub>4</sub> → N<sub>2</sub> + 2H<sub>2</sub><p></p>
The bond energies are shown in the table.<p></p>
<table class="center">
<tr>
<th>bond</th>
<th>bond energy
in kJ / mol</th>
</tr>
<tr>
<td>H–H</td>
<td>+436</td>
</tr>
<tr>
<td>N–H</td>
<td>+390</td>
</tr>
<tr>
<td>N–N</td>
<td>+160</td>
</tr>
<tr>
<td>N≡N</td>
<td>+945</td>
</tr>
</table><p></p>
What is the energy change for this reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. –339 kJ / mol<br>
<input type="radio" value="B" name="mc">
B. –97 kJ / mol <br>
<input type="radio" value="C" name="mc">
C. +97 kJ / mol<br>
<input type="radio" value="D" name="mc">
D. +339 kJ / mol<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
26. Which statement describes an exothermic reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. The energy absorbed for bond breaking is greater than the energy released by bond
formation.<br>
<input type="radio" value="B" name="mc">
B. The energy absorbed for bond breaking is less than the energy released by bond formation. <br>
<input type="radio" value="C" name="mc">
C. The energy released by bond breaking is greater than the energy absorbed for bond
formation.<br>
<input type="radio" value="D" name="mc">
D. The energy released by bond breaking is less than the energy absorbed for bond formation.<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
27. 5 g of four different fuels are set alight and placed under a beaker containing 50 cm<sup>3</sup> of water.<br>
The temperature of the water is taken at the start and after five minutes.<p></p>
Which fuel releases the most energy?<p></p>
<table class="center">
<tr>
<th> </th>
<th>temperature at start /<sup>o</sup>C </th>
<th>temperature after five minutes /<sup>o</sup>C </th>
</tr>
<tr>
<td>A</td>
<td>15 </td>
<td>23</td>
</tr>
<tr>
<td>B</td>
<td>21</td>
<td>31</td>
</tr>
<tr>
<td>C</td>
<td>28</td>
<td>47</td>
</tr>
<tr>
<td>D</td>
<td>30</td>
<td>48</td>
</tr>
</table>
<form method="post"
onSubmit="return checkAnswer(this,'C');">
<input type="radio" value="A" name="mc">
A. <br>
<input type="radio" value="B" name="mc">
B. <br>
<input type="radio" value="C" name="mc">
C. <br>
<input type="radio" value="D" name="mc">
D. <br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
28.The reaction pathway diagram for an exothermic reaction is shown.<p></p>
<img src="pic138.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
Which row identifies labels 1, 2, 3 and 4?<p></p>
<table class="center">
<tr>
<th></th>
<th>1</th>
<th>2</th>
<th>3</th>
<th>4</th>
</tr>
<tr>
<td>A</td>
<td>reactants</td>
<td>ΔH</td>
<td>E<sub>a</sub></td>
<td>products</td>
</tr>
<tr>
<td>B</td>
<td>products</td>
<td>ΔH</td>
<td>E<sub>a</sub></td>
<td>reactants</td>
</tr>
<tr>
<td>C</td>
<td>reactants</td>
<td>E<sub>a</sub></td>
<td>ΔH</td>
<td>products</td>
</tr>
<tr>
<td>D</td>
<td>products</td>
<td>E<sub>a</sub></td>
<td>ΔH</td>
<td>reactants</td>
</tr>
</table><p></p>
<form method="post"
onSubmit="return checkAnswer(this,'A');">
<input type="radio" value="A" name="mc">
A. <br>
<input type="radio" value="B" name="mc">
B. <br>
<input type="radio" value="C" name="mc">
C. <br>
<input type="radio" value="D" name="mc">
D. <br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
29. The equation for the reaction between hydrogen and chlorine is shown:
H<sub>2</sub>(g) + Cl <sub>2</sub>(g) → 2HCl (g)<p></p>
The bond energies are shown in the table.<p></p>
<table class="center">
<tr>
<th>bond</th>
<th>bond energy in kJ / mol</th>
</tr>
<tr>
<td>Cl–Cl</td>
<td>+240</td>
</tr>
<tr>
<td>H–Cl</td>
<td>+430</td>
</tr>
<tr>
<td>H–H</td>
<td>+436</td>
</tr>
</table><p></p>
What is the energy change for this reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. –1536 kJ / mol<br>
<input type="radio" value="B" name="mc">
B. –184 kJ / mol <br>
<input type="radio" value="C" name="mc">
C. +184 kJ / mol<br>
<input type="radio" value="D" name="mc">
D. +246 kJ / mol<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
30. Which arrow on the energy level diagram shows the overall energy change for an endothermic
reaction?<p></p>
<img src="pic139.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. <br>
<input type="radio" value="B" name="mc">
B. <br>
<input type="radio" value="C" name="mc">
C. <br>
<input type="radio" value="D" name="mc">
D. <br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
31. The complete combustion of propane is exothermic.<p></p>
The equation for this reaction is shown: C<sub>3</sub>H<sub>8</sub> + 5O<sub>2</sub> → 3CO<sub>2</sub> + 4H<sub>2</sub>O<p></p>
Which energy level diagram represents the complete combustion of propane?<p></p>
<img src="pic142.gif" alt="flat-dish" style="display: block; margin: 0 auto;"><p></p>
<form method="post"
onSubmit="return checkAnswer(this,'D');">
<input type="radio" value="A" name="mc">
A. <br>
<input type="radio" value="B" name="mc">
B. <br>
<input type="radio" value="C" name="mc">
C. <br>
<input type="radio" value="D" name="mc">
D. <br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
32. Nitrogen reacts with hydrogen to produce ammonia: N<sub>2</sub>+ 3H<sub>2</sub> → 2NH<sub>3</sub> <p></p>
The bond energies are shown in the table.<p></p>
<table class="center">
<tr>
<th>bond</th>
<th>bond energy in kJ / mol</th>
</tr>
<tr>
<td>N≡N</td>
<td>945</td>
</tr>
<tr>
<td>H–H</td>
<td>436</td>
</tr>
<tr>
<td>N–H</td>
<td>390</td>
</tr>
</table><p></p>
What is the energy change for this reaction?<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. –1473 kJ / mol<br>
<input type="radio" value="B" name="mc">
B. –87 kJ / mol <br>
<input type="radio" value="C" name="mc">
C. 87 kJ / mol<br>
<input type="radio" value="D" name="mc">
D. 1473 kJ / mol<br>
<input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
33. Plant cells use energy from sunlight for photosynthesis.<p></p>
Which row describes and explains the energy change that occurs?<p></p>
<table class="center">
<tr>
<th>type of energy change</th>
<th>explanation</th>
</tr>
<tr>
<td>endothermic</td>
<td>less energy is released making bonds than is absorbed to break bonds</td>
</tr>
<tr>
<td>endothermic</td>
<td>more energy is released making bonds than is absorbed to break bonds</td>
</tr>
<tr>
<td>exothermic</td>