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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>Index</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;">EXPERIMENTAL TECHNIQUES</h1>
<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. Some chemical compounds are purified by recrystallisation.<p>
What can be used to test the purity of the crystals?</p>
<form method="post"
onSubmit="return checkAnswer(this,'A');">
<input type="radio" value="A" name="mc">
A. melting point.<br>
<input type="radio" value="B" name="mc">
B. colour of crystals.<br>
<input type="radio" value="C" name="mc">
C. size of crystals.<br>
<input type="radio" value="D" name="mc">
D. solubility.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
2.The diagram shows how to obtain pure water from seawater.<br>
Where do water molecules lose energy?<p></p>
<img src="pic1.gif" alt="distillation-apparatus" style="display: block; margin: 0 auto"> <br>
<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>
3.The equation for the reaction between aqueous lead(II) nitrate and aqueous potassium iodide is
shown.<br>
Pb(NO<sub>3</sub>)<sub>2</sub>(aq) + 2KI(aq) → PbI<sub>2</sub>(s) + 2KNO<sub>3</sub>(aq)<br>
colourless colourless yellow colourless<p>
Which method could be used to separate the products?</p>
<form method="post"
onSubmit="return checkAnswer(this,'D');">
<input type="radio" value="A" name="mc">
A. chromatography<br>
<input type="radio" value="B" name="mc">
B. crystallisation<br>
<input type="radio" value="C" name="mc">
C. distillation<br>
<input type="radio" value="D" name="mc">
D. filtration
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
4.A gas Y, is less dense than air, very soluble in water and is an alkali.<br>
Which method is used to collect a dry sample of the gas?
<p></p><img src="pic2.gif" alt="gas collection-apparatus" style="display: block; margin: 0 auto"> <br>
<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>
5.The oxidation of ethanol to ethanoic acid is often carried out in the apparatus shown.<p>
What is the purpose of the condenser?</p>
<p></p><img src="pic3.gif" alt="reflux-condenser" style="display: block; margin: 0 auto"> <br>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. To prevent air reacting with the ethanoic acid.<br>
<input type="radio" value="B" name="mc">
B. To prevent any ethanol from escaping.<br>
<input type="radio" value="C" name="mc">
C. To prevent the ethanoic acid changing back to ethanol<br>
<input type="radio" value="D" name="mc">
D. To prevent the ethanoic acid reacting with the ethanol.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
6.The diagram shows copper(II) oxide being reduced, by hydrogen, to copper. After reduction is
complete, the burner is turned off but the flow of hydrogen is continued until the tube is cool.<p>
Why is the hydrogen allowed to flow through the tube during cooling?</p>
<p></p><img src="pic4.gif" alt="reduction-by-hydrogen" style="display: block; margin: 0 auto"> <br>
<form method="post"
onSubmit="return checkAnswer(this,'C');">
<input type="radio" value="A" name="mc">
A. To allow the tube to cool slowly.<br>
<input type="radio" value="B" name="mc">
B. To lessen the risk of explosion in the hot tube.<br>
<input type="radio" value="C" name="mc">
C. To prevent the copper from reacting with the air<br>
<input type="radio" value="D" name="mc">
D. To remove any traces of water left in the tube.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
7.
A fruit drink coloured orange contains a dissolved mixture of red and yellow colouring agents.<br>
One of these colouring agents is suspected of being illegal.
<p>Which method could be used to show the presence of this illegal colouring agent?</p>
<form method="post"
onSubmit="return checkAnswer(this,'A');">
<input type="radio" value="A" name="mc">
A. chromatography.<br>
<input type="radio" value="B" name="mc">
B. distillation.<br>
<input type="radio" value="C" name="mc">
C. evaporation.<br>
<input type="radio" value="D" name="mc">
D. filtration.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
8.
A student is asked to measure the time taken for 4.00 g of magnesium carbonate to react
completely with 25.0 cm<sup>3</sup> (an excess) of dilute hydrochloric acid.<p>
Which pieces of apparatus does the student need?</p>
<form method="post"
onSubmit="return checkAnswer(this,'A');">
<input type="radio" value="A" name="mc">
A. balance, clock, pipette.<br>
<input type="radio" value="B" name="mc">
B. balance, clock, thermometer.<br>
<input type="radio" value="C" name="mc">
C. balance, pipette, thermometer.<br>
<input type="radio" value="D" name="mc">
D. clock, pipette, thermometer.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
9.
A student carries out an experiment to find how fast 2 cm pieces of magnesium ribbon dissolve in
20 cm<sup>3 </sup>samples of sulfuric acid at different temperatures.
<p>Which piece of apparatus does the student <b>not</b> need?</p>
<form method="post"
onSubmit="return checkAnswer(this,'A');">
<input type="radio" value="A" name="mc">
A. balance.<br>
<input type="radio" value="B" name="mc">
B. measuring cylinder.<br>
<input type="radio" value="C" name="mc">
C. stop-clock.<br>
<input type="radio" value="D" name="mc">
D. thermometer.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
10.Lead iodide is insoluble in water.
Lead iodide is made by adding aqueous lead nitrate to aqueous potassium iodide.<p>
Which pieces of apparatus are needed to obtain solid lead iodide from 20 cm<sup>3</sup> of aqueous lead
nitrate?</p>
<p></p><img src="pic6.gif" alt="laboratory-apparatus" style="display: block; margin: 0 auto"> <br>
<form method="post"
onSubmit="return checkAnswer(this,'C');">
<input type="radio" value="A" name="mc">
A. 1, 2 and 4.<br>
<input type="radio" value="B" name="mc">
B. 1, 3 and 5 .<br>
<input type="radio" value="C" name="mc">
C. 1, 4 and 5<br>
<input type="radio" value="D" name="mc">
D. 2, 4 and 5.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
11.The table gives the solubility of four substances in ethanol and in water.<p></p>
A mixture containing all four substances is added to ethanol, stirred and filtered.
The solid residue is added to water, stirred and filtered.The filtrate is evaporated to dryness, leaving a white solid.<p>
Which is the white solid?</p>
<table class="center">
<tr>
<th rowspan ="2"></th>
<th colspan = "2">Solubility in</th>
</tr>
<tr>
<th>ethanol</th>
<th>water</th>
</tr>
<tr>
<td>A</td>
<td>insoluble</td>
<td>insoluble</td>
</tr>
<tr>
<td>B</td>
<td>insoluble</td>
<td>soluble</td>
</tr>
<tr>
<td>C</td>
<td>soluble</td>
<td>insoluble</td>
</tr>
<tr>
<td>D</td>
<td>soluble</td>
<td>soluble</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>
12.Crystals of sodium chloride were prepared by the following method.<p></p>
1. 25.0 cm<sup>3</sup> of dilute hydrochloric acid was accurately measured into a conical flask.<br>
2. Aqueous sodium hydroxide was added until the solution was neutral. The volume of
sodium hydroxide added was measured.<br>
3. The solution was evaporated and the crystals washed with approximately 15 cm<sup>3</sup> of water.<p>
Which row shows the pieces of apparatus used to measure the 25.0 cm<sup>3</sup> of hydrochloric acid, the
volume of aqueous sodium hydroxide and the 15 cm<sup>3</sup> of water?</p>
<table class="center">
<tr>
<th></th>
<th>25.0 cm<sup>3</sup> of hydrochloric acid accurately</th>
<th>the volume of aqueous sodium hydroxide added</th>
<th>15 cm<sup>3</sup> of water approximately</th>
</tr>
<tr>
<td>A </td>
<td>burette </td>
<td>pipette </td>
<td>measuring cylinder </td>
</tr>
<tr>
<td>B</td>
<td>measuring cylinder </td>
<td>burette </td>
<td>pipette </td>
</tr>
<tr>
<td>C</td>
<td>pipette </td>
<td>burette </td>
<td> measuring cylinder</td>
</tr>
<tr>
<td>D</td>
<td>pipette </td>
<td>measuring cylinder</td>
<td>burette </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>
13.
A mixture of ethanol and methanol are separated by fractional distillation.
This method of separation depends on a difference in property X of these two alcohols.
<p>What is property X?</p>
<form method="post"
onSubmit="return checkAnswer(this,'A');">
<input type="radio" value="A" name="mc">
A. boiling point.<br>
<input type="radio" value="B" name="mc">
B. colour.<br>
<input type="radio" value="C" name="mc">
C. melting point.<br>
<input type="radio" value="D" name="mc">
D. solubility.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
14.
Chromatography and fractional distillation can be used to separate compounds.
<p>In which type of separation is a thermometer needed for checking that complete separation has
occurred?</p>
<form method="post"
onSubmit="return checkAnswer(this,'D');">
<input type="radio" value="A" name="mc">
A. chromatographic separation of two colourless solids.<br>
<input type="radio" value="B" name="mc">
B.chromatographic separation of two solids of different colours.<br>
<input type="radio" value="C" name="mc">
C. fractional distillation of two colourless liquids.<br>
<input type="radio" value="D" name="mc">
D. fractional distillation of two liquids of different colours.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
15.
Which mixture can be separated by adding water, stirring and filtering?
<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. barium chloride and sodium chloride.<br>
<input type="radio" value="B" name="mc">
B. calcium carbonate and sodium chloride.<br>
<input type="radio" value="C" name="mc">
C. copper and magnesium.<br>
<input type="radio" value="D" name="mc">
D. ethane and ethene.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
16.A student investigates the speed of the reaction between a lump of zinc and an acid at room
temperature.<p>
Which other item of apparatus does the student need for this experiment?</p>
<p></p><img src="pic5.gif" alt="conical-flask-on-a-balance" style="display: block; margin: 0 auto"> <br>
<form method="post"
onSubmit="return checkAnswer(this,'C');">
<input type="radio" value="A" name="mc">
A. Bunsen burner.<br>
<input type="radio" value="B" name="mc">
B. measuring cylinder .<br>
<input type="radio" value="C" name="mc">
C. stop clock.<br>
<input type="radio" value="D" name="mc">
D. thermometer.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
17.A student wishes to extract a coloured solution from some berries to make an indicator solution.<p>
Which of the listed instructions should the student follow?</p>
<table class="center">
<tr>
<td>1 </td>
<td>crush the berries </td>
</tr>
<tr>
<td>2 </td>
<td>add acid</td>
</tr>
<tr>
<td>3 </td>
<td>add a solvent </td>
</tr>
<tr>
<td>4 </td>
<td>filter the mixture </td>
</tr>
<tr>
<td>5 </td>
<td>distil the filtrate </td>
</tr>
</table>
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. 1, 2 and 4<br>
<input type="radio" value="B" name="mc">
B. 1, 3 and 4<br>
<input type="radio" value="C" name="mc">
C. 2, 3 and 5<br>
<input type="radio" value="D" name="mc">
D. 2, 4 and 5
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
18.Which piece of apparatus should be used for the accurate measurement of 30.0 cm<sup>3</sup> of a liquid?
<form method="post"
onSubmit="return checkAnswer(this,'B');">
<input type="radio" value="A" name="mc">
A. A beaker.<br>
<input type="radio" value="B" name="mc">
B. A burette .<br>
<input type="radio" value="C" name="mc">
C. A conical flask.<br>
<input type="radio" value="D" name="mc">
D. A measuring cylinder.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
19.The reaction between solution P and solution Q is exothermic.<br>
A student is told to test this statement by mixing equal volumes of the two solutions and
measuring the temperature change.<p>
Which two pieces of apparatus should the student use?</p>
<form method="post"
onSubmit="return checkAnswer(this,'D');">
<input type="radio" value="A" name="mc">
A. balance and clock.<br>
<input type="radio" value="B" name="mc">
B. balance and thermometer .<br>
<input type="radio" value="C" name="mc">
C. pipette and clock.<br>
<input type="radio" value="D" name="mc">
D. pipette and thermometer.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
20.A coin is dissolved in an acid. Chromatography is used to test the solution formed. The diagram
shows the chromatogram obtained.<p>
What is the coin made from?</p>
<p></p><img src="pic7.gif" alt="chromatogram" style="display: block; margin: 0 auto"> <br>
<form method="post"
onSubmit="return checkAnswer(this,'C');">
<input type="radio" value="A" name="mc">
A. A metal element.<br>
<input type="radio" value="B" name="mc">
B. A non-metal element.<br>
<input type="radio" value="C" name="mc">
C. A mixture of metals.<br>
<input type="radio" value="D" name="mc">
D. A mixture of non-metals.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
21.A student mixes 25 cm<sup>3</sup> samples of dilute hydrochloric acid with different volumes of aqueous
sodium hydroxide. Each time, the student measures the change in temperature.<p>
Which piece of apparatus is <b>not</b> needed?</p>
<p></p><img src="pic8.gif" alt="laboratory-apparatus" style="display: block; margin: 0 auto"><br>
<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>
22.The outline diagrams show three methods of separation.<p>
What are the three methods called?</p>
<p></p><img src="pic9.gif" alt="distilling-flask-funnel" style="display: block; margin: 0 auto"><p> </p>
<table class="center">
<tr>
<th> </th>
<th> X </th>
<th> Y </th>
<th> Z</th>
</tr>
<tr>
<td>A</td>
<td>chromatography</td>
<td>distillation</td>
<td>filtration</td>
</tr>
<tr>
<td>B</td>
<td>distillation</td>
<td>chromatography</td>
<td>filtration</td>
</tr>
<tr>
<td>C</td>
<td>distillation</td>
<td>filtration</td>
<td>chromatography</td>
</tr>
<tr>
<td>D</td>
<td>filtration</td>
<td>chromatography</td>
<td>distillation</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>
23.A sample of a drug is analysed by using a chemical test for aspirin and measuring its melting
point.
The chemical test is positive but the melting point is 130<sup>o</sup>C , not 135 <sup>o</sup>C as it should be.<p>
What is correct?</p>
<table class="center">
<tr>
<th> </th>
<th>the sample contains aspirin</th>
<th>the sample has an impurity </th>
</tr>
<tr>
<td>A</td>
<td>yes</td>
<td>yes</td>
</tr>
<tr>
<td>B</td>
<td>yes</td>
<td>no</td>
</tr>
<tr>
<td>C</td>
<td>no</td>
<td>yes</td>
</tr>
<tr>
<td>D</td>
<td>no</td>
<td>no</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>
24.Chromatography is used to find out if a banned dye, P, is present in foodstuffs.
The results are shown in the diagram.<p>
Which foodstuff contains P?</p>
<p></p><img src="pic10.gif" alt="chromatogram" 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>
25.Mixture 1 contains sand and water.
Mixture 2 contains salt and water.<p>
Which method of separation could be used to obtain each of the required products from each
mixture?</p>
<table class="center">
<tr>
<th rowspan ="2"></th>
<th colspan = "2">mixture 1</th>
<th colspan = "2">mixture 2</th>
</tr>
<tr>
<th>to obtain sand</th>
<th>to obtain water</th>
<th>to obtain salt</th>
<th>to obtain water</th>
</tr>
<tr>
<td>A</td>
<td>crystallisation</td>
<td>distillation</td>
<td>filtration</td>
<td>filtration</td>
</tr>
<tr>
<td>B</td>
<td>crystallisation</td>
<td>filtration</td>
<td>filtration</td>
<td>distillation</td>
</tr>
<tr>
<td>C</td>
<td>filtration</td>
<td>distillation</td>
<td>crystallisation</td>
<td>filtration</td>
</tr>
<tr>
<td>D</td>
<td>filtration</td>
<td>filtration</td>
<td>crystallisation</td>
<td>distillation</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>
26.A solid metal is heated until it turns to vapour.
The graph shows the temperature of the metal during this process.<p>
Which part of the graph shows the melting of the metal?</p>
<p></p><img src="pic11.gif" alt="temperature-time-graph" style="display: block; margin: 0 auto"><br>
<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>
27.What could be the melting point and boiling point of water containing a dissolved impurity?
<p></p>
<table class="center">
<tr>
<th> </th>
<th>melting point/<sup>o</sup>C</th>
<th>boiling point/<sup>o</sup>C</th>
</tr>
<tr>
<td>A</td>
<td>+3</td>
<td>96</td>
</tr>
<tr>
<td>B</td>
<td>+3</td>
<td>104</td>
</tr>
<tr>
<td>C</td>
<td>-3</td>
<td>96</td>
</tr>
<tr>
<td>D</td>
<td>-3</td>
<td>104</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>
28.The boiling point of liquid X is lower than that of water. To test a student, a teacher covers up the
numbers on a thermometer. The student places the thermometer in boiling liquid X.<p>
The diagram represents part of the stem of this thermometer.</p>
<p>What could the temperature on the thermometer be?</p>
<img src="pic12.gif" alt="thermometer" style="display: block; margin: 0 auto"> <br>
<form method="post"
onSubmit="return checkAnswer(this,'A');">
<input type="radio" value="A" name="mc">
A. 75.5 <sup>o</sup>C<br>
<input type="radio" value="B" name="mc">
B. 84.5<sup>o</sup>C<br>
<input type="radio" value="C" name="mc">
C. 104.5<sup>o</sup>C<br>
<input type="radio" value="D" name="mc">
D. 105.5<sup>o</sup>C
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
29.
Which mixture can be separated by adding water, stirring and filtering?
<p></p>
<form method="post"
onSubmit="return checkAnswer(this,'D');">
<input type="radio" value="A" name="mc">
A. barium chloride and sodium chloride.<br>
<input type="radio" value="B" name="mc">
B. copper and magnesium.<br>
<input type="radio" value="C" name="mc">
C. diamond and graphite.<br>
<input type="radio" value="D" name="mc">
D. silver chloride and sodium nitrate.
<br><input type="submit" value="Check Answer"><input type="reset" value="Reset">
</form>
<p></p>
30.The apparatus shown cannot be used to determine the melting point of sodium chloride, Na<sup>+</sup>Cl<sup>-</sup>.<p>
Why is this?</p>
<p></p><img src="pic18.gif" alt="melting-point-apparatus" style="display: block; margin: 0 auto"> <br>
<table class="center">
<tr>
<th> </th>
<th>melting point of sodium chloride is
greater than 100<sup>o</sup>C</th>
<th>sodium chloride dissolves in the water</th>
</tr>
<tr>
<td>A</td>
<td>yes</td>
<td>yes</td>
</tr>
<tr>
<td>B</td>
<td>yes</td>
<td>no</td>
</tr>
<tr>
<td>C</td>
<td>no</td>
<td>yes</td>
</tr>
<tr>
<td>D</td>
<td>no</td>
<td>no</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>
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