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Questions and Answers

What is the empirical formula derived from the given mass ratios of the substances?

  • C2H6O (correct)
  • C6H18O3
  • C4H12O2
  • C3H9O1

How is the molecular formula related to the empirical formula based on the given molecular weight?

  • Molecular formula is equal to empirical formula times 3.
  • Molecular formula is equal to empirical formula times 2. (correct)
  • Molecular formula cannot be derived from empirical formula.
  • Molecular formula is always the same as the empirical formula.

Which of the following correctly uses the formula to calculate the number of moles from mass?

  • Number of moles = molecular mass (g/mol) / mass (g)
  • Number of moles = 12 g / mass (g)
  • Number of moles = mass (g) / 12 g/mol
  • Number of moles = mass (g) / molecular mass (g/mol) (correct)

What is Avogadro's constant used to define in the context of moles?

<p>The number of particles in one mole of substance. (C)</p> Signup and view all the answers

What is the molecular weight of the empirical formula C2H6O?

<p>46 g/mol (A)</p> Signup and view all the answers

Which statement best describes molar mass?

<p>Molar mass is the mass in grams of one mole of a substance. (C)</p> Signup and view all the answers

What is an example of a relationship established in the mole concept?

<p>The relationship between mole and mass. (B)</p> Signup and view all the answers

If the mass of a substance is 92.16 g and its molecular weight is 46 g/mol, what is the number of moles present?

<p>2 moles (D)</p> Signup and view all the answers

In the balanced equation 2Sb2O3 + 3C → 4Sb + 3CO2, which coefficient represents the number of moles of C required?

<p>3 (D)</p> Signup and view all the answers

Which equation correctly represents the relationship between coefficients in the reaction H2O + KO2 → KOH + O2 for Hydrogen?

<p>2a = c (A)</p> Signup and view all the answers

What is the unknown coefficient 'b' when balancing the equation H2O + KO2 → KOH + O2 if it is assigned the value of 1?

<p>1 (A)</p> Signup and view all the answers

How is the coefficient for O2 determined when balancing H2O + KO2 → KOH + O2?

<p>a + 2b = c + 2d (B)</p> Signup and view all the answers

In the equation K + O2 → KO2, if K has a coefficient of 'b' and O2 a coefficient of 'd', what is the correct expression for Oxygen in terms of coefficients?

<p>d = 2b (B)</p> Signup and view all the answers

In the expression 2a = c, if 'c' is known to be 1, what is the value of 'a'?

<p>0.5 (A)</p> Signup and view all the answers

What is the purpose of assigning an unknown coefficient of value 1 during the balancing process?

<p>To simplify the calculations for all coefficients (B)</p> Signup and view all the answers

When balancing reactions, which step involves writing a balanced equation for each element in terms of the unknown coefficients?

<p>Step 2 (C)</p> Signup and view all the answers

What is the molar mass of glucose C6H12O6?

<p>180 g (C)</p> Signup and view all the answers

How many molecules are in 5.23 g of C6H12O6?

<p>1.75 × 10^22 (D)</p> Signup and view all the answers

What mass corresponds to 2.8 × 10^24 atoms of iron (Fe)?

<p>259.6 g (C)</p> Signup and view all the answers

What is the correct molar mass of carbon (C)?

<p>12 g (B)</p> Signup and view all the answers

How many grams correspond to 1.94 × 10^20 molecules of Cl2?

<p>3.25 g (D)</p> Signup and view all the answers

Given that 1 mole equals $6.023 × 10^{23}$ particles, how many particles are in 1 mole of any substance?

<p>6.023 × 10^23 (B)</p> Signup and view all the answers

What relationship is used to calculate the mass when given the number of particles?

<p>Number of particles × Molar mass (C)</p> Signup and view all the answers

What is the total mass of 6.45 × 10^22 atoms of carbon (C)?

<p>25.8 g (A)</p> Signup and view all the answers

Which of the following equations correctly calculates the mass of a substance from its number of atoms?

<p>Mass = Number of atoms × Molar mass / 6.023 × 10^23 (D)</p> Signup and view all the answers

What is the unknown coefficient assigned to K2CO3 after balancing the equation?

<p>1 (C)</p> Signup and view all the answers

How is the unknown coefficient 'a' determined when balancing Al2Cl6 with KCl?

<p>It is derived from balancing Al and Cl simultaneously. (A)</p> Signup and view all the answers

After assigning coefficients in the equation Ca3(PO4)2 + H2SO4 → Ca(H2PO4)2 + Ca(HSO4)2, what is the equation for balancing oxygen?

<p>8a + 4b = 8c + 8d (C)</p> Signup and view all the answers

In the reaction Al2Cl6 → Al2(CO3)3 + KCl, what coefficient is assigned to Al2(CO3)3 after balancing?

<p>3 (C)</p> Signup and view all the answers

What is the significance of assigning a coefficient of 1 to one of the unknowns in balancing chemical equations?

<p>It is arbitrary and streamlines the balancing process. (D)</p> Signup and view all the answers

Which of the following best describes the method used for balancing the equation Ca3(PO4)2 + H2SO4?

<p>Assign unknown coefficients and solve sequentially. (C)</p> Signup and view all the answers

Which of the following elements appears only once on both sides of the equation resulting in it being balanced first?

<p>Aluminum (D)</p> Signup and view all the answers

What is the key rule when choosing the coefficient for elements occurring once on each side of the equation?

<p>They must always be equal across both sides. (B)</p> Signup and view all the answers

After resolving for coefficient 'a' in K: 2 = 6a, what is the value of 'a'?

<p>3 (D)</p> Signup and view all the answers

What is the correct stoichiometric relationship between H2O and KOH in the balanced equation?

<p>2 moles of H2O produce 4 moles of KOH (A)</p> Signup and view all the answers

In the given reaction, what is the value of the coefficient for O2 after balancing the equation?

<p>3 (B)</p> Signup and view all the answers

What is the purpose of using stoichiometric factors in a balanced chemical equation?

<p>To relate amounts of reactants to products quantitatively (A)</p> Signup and view all the answers

If carbon monoxide reacts with iron (III) oxide, what product is formed aside from iron?

<p>Carbon dioxide (A)</p> Signup and view all the answers

Which of these elements serves as the limiting reactant based on the provided reaction conditions?

<p>Carbon monoxide (D)</p> Signup and view all the answers

What is the final value of 'd' after solving the equation involving ratios?

<p>4 (C)</p> Signup and view all the answers

In stoichiometric calculations, what does the term 'stoichiometry' originate from?

<p>Greek words meaning 'element' and 'measure' (D)</p> Signup and view all the answers

What is the mass of iron produced from 152.6 g of carbon monoxide when reacting with excess iron (III) oxide?

<p>Not directly calculable without additional information (B)</p> Signup and view all the answers

What is the first step in calculating the limiting reagent?

<p>Convert the masses of reactants to moles. (B)</p> Signup and view all the answers

In the problem given, what is the stoichiometric coefficient for iron (Fe) in the balanced equation?

<p>1 (C)</p> Signup and view all the answers

Which calculation determines the limiting reagent in a reaction?

<p>The reactant with the smallest mole-to-coefficient ratio. (A)</p> Signup and view all the answers

What are the moles of sulfur (S) calculated from the given mass?

<p>0.271 mol (B)</p> Signup and view all the answers

How is the amount of moles calculated from grams for the given reactants?

<p>By using the formula: moles = grams / molar mass. (A)</p> Signup and view all the answers

After converting to moles, what value represents the limiting reagent from the calculations?

<p>0.136 for iron (Fe) (B)</p> Signup and view all the answers

If the stoichiometric coefficients were 2:1 instead of 1:1 for Fe:S, what would affect the limiting reagent?

<p>Sulfur would be favored as the limiting reagent. (A)</p> Signup and view all the answers

What is the molar mass of iron (Fe) as used in the calculations?

<p>56 g/mol (B)</p> Signup and view all the answers

Flashcards

Empirical Formula

The simplest whole-number ratio of atoms of each element in a compound.

Molecular Formula

The actual number of atoms of each element in a molecule of a compound.

Mole

A unit of measurement for the amount of a substance that contains Avogadro's number of particles.

Avogadro's Number

The number of particles (atoms, molecules, etc.) in one mole of a substance, approximately 6.02 x 10^23.

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Mole Calculation (Mass)

The formula to find moles if given mass of substance is : mass(grams) / molar mass(g/mol).

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Molar Mass

The mass of one mole of a substance (in grams/mol).

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Calculating Molecular Formula

Find the ratio of the compound's mass to the empirical formula's weight (n) to determine the whole number multiple that will give the molecular formula in respect to the empirical formula: n=(Empirical formula weight/molecular formula weight).

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Empirical formula calculation

Divide the percentage composition (or mass ratios) by the atomic weight of each elements and then, divide by the lowest result.

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Moles to Molecules Conversion

Relating the number of moles of a substance to the number of molecules it contains.

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Mole-Mass Conversion

Calculate the mass of a substance given the number of moles.

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Molar Mass of C6H12O6

The mass of one mole of glucose (C6H12O6).

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Calculating number of molecules

Determining the number of molecules given the mass and molar mass of a substance.

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Calculating mass from number of particles

Determine the mass of a substance given the number of molecules or atoms.

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Molar mass of Fe

The mass in grams of one mole of iron atoms.

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Molar mass of C

The mass in grams of one mole of carbon atoms.

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Molar mass of Cl2

The mass in grams of one mole of chlorine molecules.

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Molar mass of CO2

The mass in grams of one mole of carbon dioxide molecules.

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Balancing Chemical Equations

The process of adjusting coefficients in front of chemical formulas to ensure that the same number of atoms of each element appear on both sides of the equation.

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Coefficients in Balancing

Numbers placed in front of chemical formulas in a balanced equation to represent the number of molecules involved in the reaction.

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What is a Balanced Equation?

A chemical equation where the number of atoms of each element is the same on both the reactant and product sides.

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Step 1: Assigning Unknown Coefficients

The first step in balancing a chemical equation; involves assigning variables (e.g., 'a', 'b', 'c') to represent the unknown coefficients in front of each chemical formula.

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Step 2: Writing Balanced Equations for Each Element

The second step in balancing a chemical equation; involves setting up separate equations for each element to express the equality of atoms on both sides.

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Step 3: Assigning a Value of 1

The third step in balancing a chemical equation where we assign a value of 1 to one of the coefficients, preferably the one with the simplest relationship to other coefficients. This helps solve for other unknowns.

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Solving for Unknown Coefficients

The process of using the balanced equations and the assigned value of 1 to solve for the remaining unknown coefficients in a balanced chemical equation.

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Multiplying to Whole Numbers

The final step in balancing a chemical equation; involves multiplying the entire balanced equation by a common factor to ensure all coefficients are whole numbers.

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Balanced Chemical Equation

A chemical equation where the number of atoms of each element on both sides of the equation is equal. It represents the exact ratio of reactants and products involved in a chemical reaction.

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Stoichiometric Factors

The numerical coefficients in a balanced chemical equation that represent the relative amounts of reactants and products involved in a reaction.

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Reactant

The substances that are consumed during a chemical reaction.

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Product

The substances that are formed during a chemical reaction.

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Stoichiometry

The study of the quantitative relationships between reactants and products in chemical reactions.

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Excess Reactant

A reactant that is present in a larger amount than needed for the reaction to go to completion.

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Limiting Reactant

A reactant that is completely consumed during a chemical reaction, limiting the amount of product that can be formed.

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Calculating Mass from a Balanced Equation

Using a balanced chemical equation and molar masses, you can calculate the mass of reactants or products involved in a chemical reaction.

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Coefficient

A numerical value placed before a chemical formula in a chemical equation; indicates the number of molecules or formula units of that substance involved in the reaction.

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Law of conservation of mass

In a closed system, the total mass of matter remains constant during a chemical reaction.

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Balancing a chemical equation via inspection method

Balancing chemical equations by systematically adjusting the coefficients until the number of each atom on both sides is equal.

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Arbitrary choice of coefficient

Setting a chosen coefficient to '1' in the balancing process. This simplifies solving the balancing problem; but the actual value remains unknown.

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Step-1 in Balancing process

Assign an unknown coefficient to each substance in the chemical equation.

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Step-2 in Balancing process

Balance the equation for each element/atom using the unknown coefficients.

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Step-3 in Balancing process

Choose one unknown coefficient and set its value to 1.

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Check for balanced elements

Verify if the number of atoms for each element is equal on both sides of the equation after assigning the calculated values to the unknown coefficients.

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Multiplying through by an integer

Multiplying all the coefficients in a balanced equation by an integer to eliminate any fractions, ensuring whole numbers in the coefficients.

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Limiting Reagent (LR)

The reactant that gets completely consumed first in a chemical reaction, thus determining the amount of product formed.

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Mole Calculation

Converting the mass of a reactant in grams to moles by dividing by its molar mass.

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Stoichiometric Coefficient

The number in front of each chemical formula in a balanced chemical equation. Represents the relative number of moles of each reactant and product.

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How to find limiting reagent

Divide moles of each reactant by its stoichiometric coefficient. The smallest value corresponds to the limiting reagent.

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Impact of LR on product

The limiting reagent determines the maximum amount of product that can be formed in a chemical reaction.

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Why is finding the LR important?

Helps to calculate the theoretical yield of a reaction, optimize the use of reactants, and predict the amount of leftover reactants.

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Study Notes

Chapter 1

  • Significant figures rules for reporting measurements
  • Rules for converting units of measurement

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