Chemistry Answer Note #30

Question 1 The percentage yield of a reaction is 16.2%. If a calculated value of product that should from using the balanced chemical equation is 253.84 g, how much product will form in the actual reaction? Answer To answer this question, we first need to understand what percentage yield means in a chemical reaction. Percentage yield is a measure of the efficiency of a reaction, comparing the actual amount of product obtained to the theoretical yield, which is the maximum amount of product that can be obtained from the given reactants. In this case, the percentage yield is given as 16.2%. This means that only 16.2% of the theoretical yield was actually obtained in the reaction. To determine the actual amount of product formed, we can use the following formula: Actual yield = (Percentage yield/100) x Theoretical yield Substituting the given values, we have: Actual yield = (16.2/100) x 253.84 g = 41.14 g Therefore, the actual amount of product formed in the reaction is 41.14 g. Question 2 The percentage yield of a reaction is 74.1%. If a calculated value of product that should from using the balanced chemical equation is 56.34 g, how much product will form in the actual reaction? Answer The percentage yield of a reaction is a measure of the efficiency of the reaction, indicating the amount of desired product produced compared to the maximum theoretical yield as calculated from the balanced chemical equation. In other words, it shows the actual amount of product obtained in an experiment compared to the amount predicted by the stoichiometry of the balanced chemical equation. Using the given information, the calculated value of product that should form is 56.34 g, assuming the reaction has 100% yield. However, the given percentage yield of 74.1% indicates that the actual amount of product obtained will be less than the calculated value. To find the actual amount of product that will form in the reaction, we can use the following formula: Actual Yield = Percentage Yield x Theoretical Yield Substituting the given values, Actual Yield = 74.1% x 56.34 g = 41.72 g Therefore, the amount of product that will form in the actual reaction is 41.72 g. To further understand the concept of percentage yield and its relation to the actual and theoretical yield, here are some useful sources: In conclusion, the amount of product that will form in the actual reaction given a percentage yield of 74.1% and a calculated value of 56.34 g is 41.72 g. Understanding the concept of percentage yield is crucial in accurately determining the amount of product obtained in a chemical reaction. Question 3 How many atoms of hydrogen are there in 3.5 mol of ammonium carbonate formula units? Answer In order to accurately determine the number of hydrogen atoms present in 3.5 mol of ammonium carbonate formula units, we first need to understand the molecular formula of ammonium carbonate. According to the International Union of Pure and Applied Chemistry (IUPAC), the molecular formula of ammonium carbonate is (NH4)2CO3. Now, in one mole of any substance, there are 6.022 x 10^23 formula units. Therefore, 3.5 mol of ammonium carbonate would contain (3.5)(6.022 x 10^23) = 2.107 x 10^24 formula units. From the molecular formula, we can see that each formula unit of ammonium carbonate contains 4 hydrogen atoms. Therefore, in 2.107 x 10^24 formula units, there would be (2.107 x 10^24)(4) = 8.428 x 10^24 hydrogen atoms present. Question 4 What is the amount in moles of 158.62 g of helium? Answer To calculate the amount of substance in moles, we can use the formula n = m/M, where n represents moles, m represents mass, and M represents molar mass. Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). First, we must determine the molar mass of helium. According to the periodic table, the atomic weight of helium is 4.003 grams per mole. This means that one mole of helium has a mass of 4.003 grams. Next, we can substitute the given mass of helium (158.62 g) into the formula n = m/M. n = 158.62 g ÷ 4.003 g/mol n = 39.620 moles Therefore, the amount in moles of 158.62 g of helium is approximately 39.620 moles. Question 5 Which contains more molecules, 9.19 x 10^24 molecules of carbon dioxide or 650.00g of carbon dioxide Answer In order to determine which contains more molecules, we must first understand the relationship between molecules and mass in chemistry. Molecules are the smallest unit of a substance that retains all of its chemical properties, while mass is a measure of the amount of matter present in a substance. To answer this question, we need to convert the given quantities into a common unit, either molecules or mass, and then compare the values. Let us begin by converting 9.19 x 10^24 molecules of carbon dioxide into grams. To do so, we need to use the Avogadro's number, which is 6.022 x 10^23 molecules per mole. Therefore, 9.19 x 10^24 molecules of carbon dioxide would be equal to (9.19 x 10^24)/(6.022 x 10^23) = 15.27 moles of carbon dioxide. Next, we will use the molar mass of carbon dioxide, which is 44.01 g/mol, to convert the moles into grams. Therefore, 15.27 moles of carbon dioxide is equal to 15.27 x 44.01 = 672.53 grams of carbon dioxide. Now, let us calculate the number of molecules in 650.00g of carbon dioxide. We can start by converting the given mass into moles using the molar mass of carbon dioxide. 650.00g of carbon dioxide is equal to 650.00/44.01 = 14.76 moles of carbon dioxide. Finally, we can convert the moles into molecules using Avogadro's number. 14.76 moles of carbon dioxide is equal to (14.76 x 6.022 x 10^23) = 8.89 x 10^25 molecules of carbon dioxide. Based on these calculations, we can clearly see that 650.00g of carbon dioxide contains a greater number of molecules, 8.89 x 10^25 molecules, compared to 9.19 x 10^24 molecules in 9.19 x 10^24 molecules of carbon dioxide. Therefore, 650.00g of carbon dioxide contains more molecules than 9.19 x 10^24 molecules.