Resitasi Kimia Dasar : Stoikiometri Bagian 2

Summary

This educational video explains key concepts in stoichiometry, focusing on empirical formulas and reaction yields. It covers topics like the relationship between reactants and products in chemical reactions, how to calculate the empirical formula of compounds from given mass data, and how to determine reaction yields using theoretical and actual results. Various examples demonstrate how to calculate moles, determine empirical and molecular formulas, and understand limiting reagents in reactions. The video concludes with exercises for calculating the number of atoms in a given mass of a substance and determining the empirical formula of a compound.

Takeaways

• 😀 The empirical formula represents the simplest ratio of atoms of each element in a compound, e.g., glucose has the formula C6H12O6, but the empirical formula is CH2O.
• 😀 Reactants are the substances that undergo chemical reactions, while products are the substances formed as a result of the reaction.
• 😀 To calculate the required or produced amounts of substances in a reaction, one must write the balanced equation, calculate the mol of known substances, and use the coefficient ratio from the equation.
• 😀 Reaction yield is used when results don't exactly match the theoretical predictions. The theoretical yield is the expected amount, while the actual yield is the measured amount.
• 😀 To calculate reaction yield, the formula is: Reaction Yield (%) = (Actual Yield / Theoretical Yield) × 100.
• 😀 In an example problem involving chromium oxide (Cr2O3), the empirical formula is determined by comparing the number of moles of chromium and oxygen in the compound.
• 😀 For primidine, the empirical formula is found by calculating the molar ratio of carbon, hydrogen, and nitrogen from the given percentages of the elements and their atomic masses.
• 😀 The molecular formula of a compound is determined by comparing the molar mass of the empirical formula to the molecular mass. If the molar mass is a multiple, the empirical formula is multiplied accordingly.
• 😀 In a combustion reaction of carbon with oxygen to produce CO, stoichiometry is used to calculate the required amounts of oxygen and the mass of carbon monoxide produced.
• 😀 For a reaction involving hydrogen and oxygen to form water, the percentage yield can be calculated by comparing the actual mass of water produced to the theoretical mass based on stoichiometry.

Q & A

What is an empirical formula?

An empirical formula is the simplest ratio of the elements in a compound, showing the relative number of atoms of each element in the simplest whole number ratio.

How is the empirical formula of glucose, C6H12O6, determined?

The empirical formula of glucose is CH2O. This is determined by dividing each element's atom count in the molecular formula (C6H12O6) by 6, which simplifies the ratio to 1:2:1 for carbon, hydrogen, and oxygen respectively.

What is the difference between reactants and products in a chemical reaction?

Reactants are the substances that undergo a chemical reaction, while products are the substances formed as a result of that reaction.

What is the reaction yield, and how is it calculated?

The reaction yield refers to the efficiency of a chemical reaction, comparing the actual amount of product obtained to the theoretical amount. It is calculated using the formula: (actual yield / theoretical yield) * 100.

How is the empirical formula for chromium oxide (Cr2O3) determined?

The empirical formula of chromium oxide is determined by calculating the moles of chromium and oxygen from the given masses, finding the simplest ratio of moles between the elements, and using this ratio to determine the formula.

How is the molecular formula of primidine determined?

To determine the molecular formula of primidine, the empirical formula is first calculated based on the percentage composition of carbon, hydrogen, and nitrogen. Then, the molar mass of the empirical formula is compared to the molecular mass of the compound, and the empirical formula is multiplied by a factor to match the molecular mass.

How is the number of atoms in a given mass of a substance calculated?

The number of atoms in a given mass of a substance is calculated by first determining the moles of the substance using its molar mass, and then multiplying the moles by Avogadro's number (6.022 × 10^23 atoms per mole).

What is the significance of the balanced equation C + O2 → CO?

The equation shows that carbon reacts with oxygen to form carbon monoxide. The balance of the equation ensures that the number of atoms of each element is conserved during the reaction.

How is the theoretical yield of water calculated in the reaction of hydrogen and oxygen?

The theoretical yield of water is calculated by determining the moles of hydrogen used in the reaction, then using the stoichiometric ratio from the balanced equation to find the moles of water produced. The mass of water is then found by multiplying the moles by its molar mass.

How is the empirical formula of allicin (found in garlic) calculated?

The empirical formula of allicin is calculated by converting the given mass percentages of carbon, hydrogen, sulfur, and oxygen into moles, then finding the simplest whole number ratio of these moles to determine the empirical formula.