CHM 143 Lecture Notes - Lecture 8: Greatest Common Divisor, Chemical Formula, Molar Mass

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27 Sep 2016

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Determine the empirical formula for methylbutyrate if the % composition by mass is. Whole # ratio of the # moles of each element: calculatte #moles of each element using mass , convert to whole # ratio. Mass percent means for every 100g of compound cxhyoz that 58. 80g c, 9. 87g h, and 31. 33 g o will be present. The combined (sum) of mass % of the elements should add up to 100% and combined masses should add up to 100g. Calculations: 58. 80g c x mole c = 4. 85959 mol c. 9. 87 g h x mole h = 9. 7722 mol h. 31. 33 g o x mole o = 1. 9581 mol o. Convert to whole number ratio, divide all by lowest number of moles: 2. 5 c, 5. 0 h, 1. 00 o. This is the lowest ratio of atoms with the lowest # of 1. But cannot have 2. 5 as a subscript in a chemical formula.

Related Questions

Please explain also

Determine the simplest whole number mole ratio of C,H and O in the unknown using the 5 of 6 character format such as C2H30, C3H40, C2H3O2, etc. If a coefficent for a given element is 1, omit it from the empirical formula.

State the answer as CxHyOz - ?

Mass of O - 0.8246g Moles of O - 0.05

Moles of H atoms - 0.172 moles Moles of C atoms - 0.050

Moles of H2O - 0.086 moles Moles of CO2 - 0.050

Compare the moles of C, moles of H and moles of O and determine which value is the smallest. Now take the moles of each atom (C, H, and O) and divide each by the smallest value. The whole number that you get for each atom will give you the empirical formula for catechol.

1. Consider the unbalanced equation for the reaction of solid lead with a silver nitrate solution.

_____Pb (s) + ______AgNO3 (ac) â ______Pb(NO3)2 (ac) + _______Ag (s)

a. Balance the equation.

b. How many moles of silver nitrate are required to react completely with 9.3 mol of lead?

c. How many moles of silver, Ag, are formed by the complete reaction of 28.4 mol of Pb?

2. For the following reaction: _____CaO (s) + _____CO2 (g) â _____CaCO3 (s), Calculate how many grams of CaCO3, are formed when 2.4 g of CaO Do they react completely with CO2?

3. For the following reaction: 2 Li (s) + F2 (g) â 2 LiF (s), find the reagent limiting with the amounts of 1.0 mol of Li and 1.0 mol of F2.

4. For the next reaction, determine the limiting reagent, calculate the yield Theoretical product in grams with 5.5 g of Al and 19.8 g of Cl2.

2 Al (s) + 3 Cl2 (g) â 2 AlCl3 (s)

5. Consider the reaction between NiS2 and O2:

2 NiS2 (s) + 5 O2 (g) â 2 NiO (s) + 4 SO2 (g)

When 11.2 g of NiS2 react with 5.43 g of O2, 4.86 g of NiO are obtained. Determine the limiting reagent, the theoretical yield of NiO and the% yield for the reaction.

6. How many atoms of mercury are in 5.8 mol of mercury?

7. Complete the following table:

Element Moles Mass Number of molecules

8. How many grams of sodium are there in 1.00 g of each of the following compounds?

a. Na3PO4

b. NaC7H5O2

c. Na2C6H6O7

9. A sample of 4.78 g of aluminum reacts completely with oxygen to form 6.67 g of aluminum oxide. Use the data to calculate the percent of composition by mass.

10. Citric acid, the compound responsible for the bitter taste in lemons, has the following composition: C - 37.51%

H - 4.40%

O - 58.29%

Calculate the empirical formula.

11. A compound containing phosphorus and oxygen has a molar mass of 219.9 g / mol and an empirical formula of P2O3. Find the molecular formula of compound.

12. It is a term used in chemistry, to describe a system in which a

or more substances, are mixed or dissolved homogeneously in another

substance.

a. Mixture

b. Solution

c. Compound

d. None of the above

13. It is the component that is in a solution, in smaller quantity.

a. Solution

b. Solvent

c. Solvent

d. Soluto

14. It is the component that is in a solution in greater quantity.

a. Solution

b. Solvent

c. Solvent

d. The answers b and c are correct.

15. The quantitative expression of the dissolved amount of solute in a quantity determined solvent is known as:

a. Solution

b. Volume

c. Concentration

d. Stoichiometry

16.Express the moles of solute among the liters of solution

a. Molality

b. Molarity

c. % weight by volume

d. % weight by weight

17.Express the moles of solute between kg of solvent

a. Molarity

b. ppm

c. ppt

d. Molality

18. What is the molarity of a solution prepared by dissolving 7.50 g of nitrate of magnesium, Mg (NO3) 2 in enough water to prepare 25.0 mL of solution?

a. 10.3 M

b. 5.6 M

c. 6.5 M

d. 2.03 M

19. How many grams of sodium chloride, NaCl are needed to prepare 125 mL of 0.037 M NaCl solution

a. 1.021 M

b. 0.268 M

c. 0.201 M

d. 0.500 M

20. Calculate the molality of a solution containing 12.5 g of ethylene glycol (C2H6O2) dissolved in 135 g of water.

21. A solution of ethylene glycol contains 21.2 g of ethylene glycol (C2H6O2) in 85.4 mL of water. Calculate the freezing point and the boiling point of the solution. (Assume the water density is 1.00 g / mL)

22. At what volume should you dilute 75 mL of a 10.0 M solution of H2SO4 to obtain a 1.75 M solution of H2SO4.

CHM 143 Lecture Notes - Lecture 8: Greatest Common Divisor, Chemical Formula, Molar Mass

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