i am working on a practice worksheet and need help with a few i can not understand. please and thank you. I have to post them separately sorry
49.how many grams of water are needed to completely hydrolyze 30.8 g of the ester?
A.0.416 g
B.30.8 g
C.11.3 g
D.7.49 g
54. Sodium stearate is a soap that is produced from stearic acid, one of the fatty acids.
stearic acid sodium stearate
The reaction that was set up with 0.25 g stearic acid and an excess of sodium hydroxide produced 0.25 g soap. The percent yield was
A.93%.
B.100%.
C.25%.
D.1%.
56. While this isn't a real reaction, we can say that carbonic acid, H2CO3, can be produced directly from the elements. Choose the statement that is correct when the given masses are supplied to react.
2H2+ 2C+ 3O2=2H2CO3
47g 282g 940g
A.There is no limiting reactant.
B.Carbon is the limiting reactant.
C.Oxygen is the limiting reactant.
D.Hydrogen is the limiting reactant.
number 56 answer is oxygen is the limiting reactant
49. To determine the grams of water needed to completely hydrolyze the ester, you need to use the balanced equation for the hydrolysis reaction. Unfortunately, that equation is not provided in the question. Without the balanced equation, it is not possible to determine the exact grams of water required. Therefore, this question cannot be answered with the information given.
54. The percent yield is calculated by dividing the actual yield by the theoretical yield, and then multiplying by 100.
Actual yield: 0.25 g
Theoretical yield: the maximum amount of soap that can be produced from the given amount of stearic acid.
Since it is mentioned that there is an excess of sodium hydroxide, it means that all the stearic acid would react to form soap. Therefore, the theoretical yield is also 0.25 g.
Percent yield = (actual yield / theoretical yield) × 100
Percent yield = (0.25 g / 0.25 g) × 100 = 100%
Therefore, the correct answer is B. 100%.
56. To determine the limiting reactant, compare the given masses of each element with the stoichiometric ratio provided in the balanced equation.
Stoichiometric ratio (according to the balanced equation):
2H2 + 2C + 3O2 → 2H2CO3
Given masses:
Hydrogen (H2): 47 g
Carbon (C): 282 g
Oxygen (O2): 940 g
To determine the limiting reactant, calculate the number of moles of each element using their molar masses (H2: 2 g/mol, C: 12 g/mol, O2: 32 g/mol) and then compare the moles to the stoichiometric ratio.
Hydrogen (H2):
moles = mass / molar mass = 47 g / 2 g/mol = 23.5 mol
Carbon (C):
moles = mass / molar mass = 282 g / 12 g/mol = 23.5 mol
Oxygen (O2):
moles = mass / molar mass = 940 g / 32 g/mol = 29.375 mol
Comparing the moles of each element to the stoichiometric ratio, it can be observed that the lowest number of moles is found for hydrogen (H2). Therefore, hydrogen is the limiting reactant.
The correct answer is D. Hydrogen is the limiting reactant.
To solve these questions, you will need to use stoichiometry, which is a method for calculating the quantities of reactants and products in a chemical reaction. Here's how you can approach each question:
49. To find out how many grams of water are needed to hydrolyze the given amount of ester, you need to set up and balance the chemical equation for the hydrolysis reaction. The balanced equation will tell you the mole ratio between the ester and water. Then, using the molar mass of water, you can convert the moles of water to grams.
54. The percent yield is calculated by dividing the actual yield by the theoretical yield, and then multiplying by 100. In this case, the actual yield is given as 0.25 g of soap, and the theoretical yield can be calculated by stoichiometry using the balanced equation for the reaction. By comparing the actual yield to the theoretical yield, you can determine the percent yield.
56. To determine the limiting reactant in this reaction, you need to compare the number of moles of each reactant to the stoichiometric coefficients in the balanced equation. The reactant that has the smallest number of moles compared to the stoichiometric coefficients is the limiting reactant. In this case, you will need to convert the given masses of each reactant to moles and then compare them.
It's important to note that you haven't provided the balanced chemical equations for these reactions in your question, so I am unable to provide you with the specific steps and calculations. Once you have the balanced equations, you can follow the steps outlined above to solve each question.