Assignment: Empirical formula and typical question related mathematical problem.
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The document is an assignment for a chemistry course focusing on empirical and molecular formulas based on given percentage compositions of various compounds such as benzoic acid, acetic acid, acetaldehyde, and oxalic acid. It also explains the distinction between elements and compounds, concepts of precision in measurements, and rules for determining significant figures in calculations. Additionally, it provides examples of elements, compounds, heterogeneous and homogeneous mixtures, as well as exercises involving significant figures.
Assignment: Empirical formula and typical question related mathematical problem.
- 1. BGMEA University of Fashion & Technology Department of Apparel Manufacturing & Technology Course Code: CHEM-1101 Course Title: Chemistry Assignment Assignment Name: Empirical formula and typical question related mathematical problem. Submitted To: Submitted By: Dr. Md. Mohibul Islam Khan Prosanto Saha Assistant Professor ID: 201-120-101 BUFT Batch:201, AMT-3
- 2. 1. Benzoic acid is a white, crystalline powder used as a food preservative. The compound contains 68.8% C, 5.0% H, and 26.2% O, by mass. What is its empirical formula? Lat’s consider the total weeight of the gass composition is 100 The molar amount of, C= . = 5.7333 The molar amount of, H= . = 5.0 The molar amount of, O= . = 1.63 The molar ratio of, C= . . = 3.501≅ 3.5 The molar ratio of, H= . = 3.053~3 The molar ratio of, O= . . = 1 Thus, the empirical formula benzoic acid is C3.5H3O = (C3.5H3O)2 =C7H6O2
- 3. 2. We found the percentage composition of acetic acid to be 39.9% C, 6.7% H, and 53.4% O. Determine the empirical formula. The molecular mass of acetic acid was determined by experiment to be 60.0 amu. What is its molecular formula? Given that, Lat’s consider the total weeight of the gass composition is 100 The molar amount of, C= . = 3.32 The molar amount of, H= . = 6.7 The molar amount of, O= . = 3.33 The molar ratio of, C= . . = 1 The molar ratio of, H= . . = 2.02 ≅ 2 The molar ratio of, O= . . = 1 The empirical formula of the composition is= 𝐶𝐻2O The molecular mass of acetic acid is 60.0 amu Since, the empirical formula is CH2O the molecular formula will be (CH2O)n= CnH2nOn The mass of empirical formula of the compound stands=(12+1×2+16)=30 and molecular mass 60.
- 4. Therefore, n= n= = 2 Thus, the molecular formula the compound is C2H4O2 3. The percentage composition of acetaldehyde is 54.5% C, 9.2% H, and 36.3% O, and its molecular mass is 44 amu. Obtain the molecular formula of acetaldehyde. Lat’s consider the total weeight of the gass composition is 100 The molar amount of, C= . = 4.54 The molar amount of, H= . = 9.2 The molar amount of, O= . = 2.26 The molar ratio of, C= . . = 2 The molar ratio of, H= . . = 4 The molar ratio of, O= . . = 1 The empirical formula of the composition is=C2H4O The molecular mass of acetic acid is 44 amu
- 5. Since, the empirical formula is C2H4O the molecular formula will be (C2H4O)n The mass of empirical formula of the compound stands=(12×2+1× 4 +16)=44 and molecular mass 44. Therefore, n= n= = 1 Thus, the molecular formula the compound is C2H4O 4. Oxalic acid is a toxic substance used by laundries to remove rust stains. Its composition is 26.7% C, 2.2% H, and 71.1% O (by mass), and its molecular mass is 90 amu. What is its molecular formula? Lat’s consider the total weeight of the gass composition is 100 The molar amount of, C= . = 2.225 The molar amount of, H= . = 2.2 The molar amount of, O= . = 4.44
- 6. The molar ratio of, C= . . = 1 The molar ratio of, H= . . = 1 The molar ratio of, O= . . = 2 The empirical formula of the composition is= 𝐶𝐻O2 The molecular mass of the compound is 90 amu Since, the empirical formula is CHO2 the molecular formula will be (CHO2)n= CnH2nOn The mass of empirical formula of the compound stands=(12+1+16× 2)=45 and molecular mass 90. Therefore, n= n= = 2 Thus, the molecular formula the compound is C2H2O4
- 7. 5. Give examples of an element,a compound,a heterogeneous mixture, and a homogeneous mixture. Element: Element are the pure substances containing only one kind of atoms. Example: Iron is made of iron atoms so iron can be defined as elements. Compound: Any substance composed of identical molecules consisting of atoms of two or more chemical elements can be called compound. Example: Water is a compound because it is made up of more than one element-hydrogen and oxygen. Example of Heterogeneous Mixture: i. Concrete is heterogeneous mixture of an aggregate cement & water. ii. Ice cubes in cola from a heterogeneous mixture. Example of Homogeneous Mixture: Homogeneous mixture can be defined as solid mixture,liquid mixture,gaseous mixture. Such like: sugar water,sodas,bronze,blood plasma,dishwashwashing detergents.
- 8. 6. What distinguishes an element from a compound? Can a compound also be an element? Elements are pure substances and they are composed of only one type of atom and compounds are formed by two or more different types of elements that are united chemically in fixed proprotions and it is the main way to distinguish elements from compound. A pure element cannot be a compound. 7. What is meant by the precision of a measurement? How is it indicated? The precision of a measurement system is refers to how close the agreement is between to how close the agreements is between repeated measurements which are repeated measurements which are repeated under the same conditions. One way to analyze the precision of the measurement would be to determine the range or difference between the lowest and highest measured values. In that case, the lowest value is 10.9 in and the highest value is 11.2 in.
- 9. 8. Two rules are used to decide how to round the result of a calculation to the correct number of significant figures. Use a calculation to illustrate each rule.Explain how you obtained the number of significant figures in the answers? •Procedure to determine significant figures after multiplication or division: 1. Multiply or divide the numbers using our calculator. 2. Round the result to have the same number of significant figures as the measured value with the least number of significant figures. • Below are two examples. A) Write the product of 2.10 × 0.5896 with the correct number of significant figures. Step 1) 2.10 × 0.5896 = 1.23816 Step 2) 1.23816 = 1.24 (three sig. figs because 2.10 has three) The answer is 1.24 B) Write the quotient of 16.15/2.7 with the correct number of significant figures. Step 1) 16.15 / 2.7 = 5.98148148 Step 2) 5.98148148 = 6.0 (two sig. figs because 2.7 has two) The answer is 6.0
- 10. 9. Consider three masses that you wish to add together: 3 g,1.4 g, and 3.3 g.These numbers represent measured values.Add the numbers together and report your answer to the correct number of significant figures? The three given masses are 3.0g,1.4g, and 3.3g Add the together and we get= (3.0+1.4+3.3)g =7.7g After adding the mass values the result value 7.7 Contain two significant numbers. 10. How many significant figures are there in each of the following measurements? a. 73.0000 g b. 0.0503 kg c. 6.300 cm d. 0.80090 m e. 2.010 s a) 7.30000- significant figures -6 b) 0.0503- significant figures -3 c) 6.300- significant figures -4 d) 0.80090- significant figures -5 e) 2.010- significant figures -4