CHE301 Midterm Solved Subjective

CHE 301 Midterm Solved

Qno1. What do you know about pareto diagram? 2marks

Pareto Diagram • is a combination of bar and line graphs of accumulated data Pareto Diagram • is a combination of bar and line graphs of accumulated data Benefits • Breaks big problem into smaller pieces

• Identifies most significant factors
• Shows where to focus efforts
• Allows better use of limited resources

Qno2. Name the sources of errors? 3marks

Sources of error

Instrumental Error

If a balance weigh 2 g as 2.1 g. • If a 10 mL pipette draw a volume of 9.5 mL on average • If a faulty pH meter read 4.0 pH buffer as 4.21 even after calibration • Leakage in burette

• If a method say
• heat it
• stay at room temperature
• Use buffer of pH 10 Note: The meaning of such statements may be different for different analyst

Human Error (Personnel error)

• If a personnel
• Problem in identifying colour / meniscus
• Don’t follow procedure properly
• Careless behavior in calibration
• Note the meniscus above or below eye level

Qno3. Write down the Goals of sampling. 2marks

Goals of Sampling To obtain a mean analyte concentration Unbiased estimate of the population mean. Every possible sample is equally and likely to be drawn.

Qno4: What is limit of quantization? 2marks

Quantization limit • Based on Visual Evaluation • Based on SNR • Based on STD Dev

Qno5: How equipment can be calibrated? 3marks

Calibration of Equipment

•Calibration of an analytical balance using standard weights

• Calibration of pipette / micropipettes and other volumetric apparatus to SI units using a calibrated balance
• Calibration of pH meter with standard buffers

Qn6: Give the sequence of quality assurance from SI units to products. 2marks

SI Units National ->physical standards (NPSL)-> Accredited calibration laboratory (reference standard) - > In-house calibration laboratory (working standard)-Measuring and test equipment-> Product

Qno7: Colloidal suspension crystalline suspension? 3marks

1-Colloidal suspensions

• Particles are invisible to the naked eye (10-7 - 10-4 cm in diameter).
• Colloidal particles show no tendency to settle from solution
• Not easily filtered. 2-Crystalline suspension
• Particles with dimensions on the order of tenths of a millimeter or greater.
• The temporary dispersion of such particles of a tend to settle spontaneously,
• Easily filtered.

Qno8: Classification of gravemetric analysis? 5marks

Classification of gravimetric analysis

1. Precipitation gravimetry

2. Volatilization gravimetry 3. Electrogravimetry Precipitation Gravimetry

• The analyte is converted to a sparingly soluble precipitate which is then filtered, washed (free of impurities), converted to a product of known composition by suitable heat treatment, and weighed.
• For example, a precipitation method for determining calcium in natural waters. The reactions are: 2NH3 + H2C2O4 2NH4+ + C2O4-2 Ca+2(aq) + C2O4-2 (aq) CaC2O4 (s)

Precipitation Gravimetry (Continued)

• The precipitates are filtered using a weighed filtering crucible, then dried and ignited to converts the precipitate to calcium oxide. The reaction is: CaC2O4 (s) CaO (s) + CO (g) + CO2
• After cooling, the crucible and precipitate are weighed, and the mass of calcium oxide is determined by subtracting the known mass of the crucible. The calcium content of the sample is then computed.

Qno9: Define Analytical Chemistry. 2marks

Analytical Chemistry is basically study of testing methods for determining composition of substances. This determination may be limited to qualitative results or quantitative estimation. Qualitative means what substances are present in composition.

Qno10: Explain the two examples of Scatter Diagram. 3marks

Examples of Scatter diagram

• Relationship between thermal treatment temperature of a steel material and its tensile strengths
• Relationship between visit made by a salesman and volume of sales
• Relationship between the number of persons visiting a department store and volume of sales

Qno11: Difference between Quality control and Quality assurance. 3marks

Qno12: How we prepared sample? 5marks

From 100 of Kg, 1000 of litters or acres of land we collect the sample in grams. And to analyse we have to finalize just 2-3 gram of sample, or maximum 100 mL of liquid. Some time sample need dilution while some