It is important to compare the positive and negative test results with those of known compounds as positive results indicate the presence of that known compound and negative results indicate the absence of that compound which is used for reference.
<h3>What is qualitative analysis?</h3>
Qualitative chemical analysis is a method to determine the chemical composition of a sample.
There are two types of qualitative analysis:
- Organic Qualitative analysis: It helps in determining the chemical bonds and functional groups in a sample
- Inorganic qualitative analysis: It helps in determining the ions in the given sample
There are seven ways to analyze a sample qualitatively, which are
A reference compound is always used to which results are compared.
A Positive result indicates that the reference compound is present in the sample whereas a negative result indicates that the reference compound is absent in the given sample.
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Part 1 : Answer is only B substance is soluble in water.
In this experiment undissolved mass of each substance was measured. According to the given data, undissolved mass of substance B at 20 °C is 10 g while A is 50 g. Since, the initial added mass of each substance is 50 g, we can see that substance A is not soluble in water since the undissolved mass is 50 g.
Part 2 : Substance A is not soluble in water and substance B is soluble in water.
According to the given data, the undissolved mass of substance A remains as same as initial added mass, 50 g throughout the temperature range from 20 ° to 80 °C. Hence, we can conclude that substance A is not soluble in water.
But, according to the data, undissolved mass of substance B at 20 °C is 10 g. That means, 40 g of substance B was dissolved in water. When the temperature increases the undissolved mass of substance B decreases. Hence, we can conclude that substance B is soluble in water and solubility increases with temperature.
To solve this we use the
equation,
M1V1 = M2V2
<span>where M1 is the concentration of the stock solution, V1 is the
volume of the stock solution, M2 is the concentration of the new solution and
V2 is its volume.</span>
4.5 ( V1 ) = 3.0 ( 500 mL )
V1 = 333.33 mL needed of the 4.5 M phosphoric acid
Hope this answers the question. Have a nice day.
