Chemistry: Ionic Equations and Moles

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Questions and Answers

What does it mean when ions separate in a solution?

The substance dissociates into its constituent ions. (correct)

The substance becomes non-ionic.

The substance forms a solid precipitate.

The substance remains intact.

In the reaction of FeSO4 with 2NaOH, which ions are considered spectator ions?

Fe2+ and Na+

Na+ and SO42- (correct)

Na+ and OH-

Fe2+ and SO42-

Which of the following is the correct formula to find the number of moles based on mass and molecular weight?

Moles = Mass / Mr (correct)

Moles = Mr / Mass

Moles = Mass × Mr

Moles = Mass + Mr

What happens to the CaCO3 when it is heated according to the reaction provided?

It decomposes into CaO and CO2. Signup and view all the answers

When converting litres to cm3, what is the conversion factor used?

1000 Signup and view all the answers

In the equation FeSO4 (aq) + 2NaOH(aq), which state symbol indicates a solid product?

(s) Signup and view all the answers

What is the main purpose of writing a chemical equation in ionic form?

To identify spectator ions. Signup and view all the answers

If 20g of CaCO3 is provided, how is this information relevant to calculations involving moles?

It allows for the calculation of the number of moles present. Signup and view all the answers

What is the empirical formula of the compound formed when 6 moles of potassium react with 3 moles of oxygen?

K2O Signup and view all the answers

How many moles of sulfur are there in 32 grams when reacting with 6 grams of carbon?

1 mole Signup and view all the answers

What is the first step in calculating the empirical formula using mass?

Convert mass to moles Signup and view all the answers

When finding the empirical formula from moles, what is the next step after determining the mole ratio?

Divide each value by the smallest number of moles Signup and view all the answers

If 6g of carbon reacts with 32g of sulfur, what is the empirical formula of the resulting compound?

CS2 Signup and view all the answers

What does EF stand for in the context of chemical compounds?

Empirical Formula Signup and view all the answers

In the formula for calculating moles, what does 'Ar' stand for?

Atomic Mass Signup and view all the answers

Which of the following is commonly examined when determining empirical formulas?

Calculating from percentage composition Signup and view all the answers

What characterizes a balanced chemical equation?

It contains the same number of atoms of each element on both sides. Signup and view all the answers

When balancing chemical equations, which of the following is acceptable?

Adjust the coefficients in front of the formulae. Signup and view all the answers

Which of the following is an example of a covalent compound?

Hydrogen peroxide. Signup and view all the answers

What would be the proper coefficient in front of HCl when balancing the equation CaCO3 + HCl -> CaCl2 + H2O + CO2?

2 Signup and view all the answers

Which ion is found in hydrogen peroxide and is considered special?

Peroxide ion (O2^2-) Signup and view all the answers

What might be necessary when balancing an equation aside from changing coefficients initially?

Adjusting coefficients multiple times during the process. Signup and view all the answers

Why can’t the formula of a compound be changed when balancing an equation?

It would result in a completely different reaction. Signup and view all the answers

Which of the following describes a necessary skill before balancing chemical equations?

Being able to work out chemical formulae accurately. Signup and view all the answers

What happens to the anion in the presence of a cation with a large charge density difference?

The anion becomes distorted by the cation's pull. Signup and view all the answers

What do permanent dipoles in molecules lead to?

Inter-molecular forces between molecules. Signup and view all the answers

Which of the following describes the effect of Fajan's Rules?

Ion charge and size influence covalent character in ionic compounds. Signup and view all the answers

Which of the following types of intermolecular forces involves attractions between opposite charges?

Permanent dipole – Permanent dipole attraction. Signup and view all the answers

What characteristic of molecules contributes to polarization according to Fajan's Rules?

Size and charge of the ions. Signup and view all the answers

Which option best describes the interaction that leads to inter-molecular forces in polar molecules?

Negative parts of one molecule attract positive parts of another. Signup and view all the answers

What contributes to the covalent character in ionic compounds as per Fajan's Rules?

Large differences in charge density of ions. Signup and view all the answers

What is not a type of intermolecular force?

Covalent bonding. Signup and view all the answers

What is the empirical formula for a compound made of 2 moles Na and 2 moles I?

NaI Signup and view all the answers

Which of the following represents the empirical formula for a compound with 0.5 moles N and 1.5 moles H?

NH3 Signup and view all the answers

Determine the percentage composition by mass of oxygen in a compound with 12g C and 16g O.

57.14% Signup and view all the answers

What is the empirical formula of a compound that consists of 6g Mg with 4g O?

MgO Signup and view all the answers

Which of the following compounds has a formula for 1.2 moles of a carbon oxide containing 0.4 moles of carbon?

CO Signup and view all the answers

What is the correct empirical formula for a compound made of 0.1 moles K and 0.05 moles O?

KO Signup and view all the answers

For a compound containing 3g of an element X and 0.5 moles of element Y, which of the following is the correct empirical formula if Y is 12g?

XY Signup and view all the answers

What is the empirical formula for 0.2 moles Mg and 0.4 moles Cl?

MgCl2 Signup and view all the answers

What occurs to metal atoms during metallic bonding?

They lose their outer electron(s) to become cations. Signup and view all the answers

What role do delocalised electrons play in metallic bonding?

They hold the metal structure together through electrostatic attraction. Signup and view all the answers

What model describes the arrangement of electrons in metallic bonding?

Sea of electrons model. Signup and view all the answers

Which of the following statements about metallic bonding is true?

Cations are surrounded by an electron sea. Signup and view all the answers

What defines the term 'delocalised' in the context of metallic bonding?

Electrons are able to freely move throughout the metal. Signup and view all the answers

What is the main characteristic of the electron sea model?

Electrons are free to move around positively charged ions. Signup and view all the answers

How does metallic bonding differ from pure ionic bonding?

Metallic bonding includes delocalised electrons instead of localized ones. Signup and view all the answers

What is one important property resulting from metallic bonding?

High electrical conductivity. Signup and view all the answers

Study Notes

Moles and Formulae

To succeed with this topic, students need to be able to find atomic mass (A) from the periodic table and know basic arithmetic. They will also be able to calculate molecular mass (M) from A values, percentage composition by mass for a compound, moles from grams and grams to moles of a substance, empirical formulae and molecular formulae.

Finding M (relative molecular mass or formula mass)

The Molecular Mass or Formula Mass (M) of a compound is found by adding the relative atomic masses (A) of the elements in the compound's formula, from the periodic table.
The small number outside brackets in a formula multiplies all elements inside the parentheses.

Percentage composition of a compound

To calculate the percentage composition by mass of an element in a compound:
- Calculate the relative formula mass (M) of the compound
- Divide the total atomic mass of the given element by the overall M of the compound, then multiply by 100%

Moles

A mole of a substance is 6.023 x 10²³ particles.
The Avogadro number (6.023 x 10²³) is the number of particles in 1 mole of a substance.
The mass of 1 mole of a substance (in grams) is equal to the relative atomic mass (A) or relative formula mass (M).

Calculations with Moles

Number of moles = mass (g) / (A or M)
Mass (g) = moles x (A or M)
(A or M) = mass (g)/ moles

Finding Empirical Formulae

There are several methods to calculate empirical formulae.

Calculating Empirical Formula from Moles

Relative ratios of moles are equal to relative ratios of elements that make up the compound.

Calculating Empirical Formula from Mass

Relative ratios of moles of elements to elements in the compound can be found by dividing the mass of each element concerned by its atomic mass (A) from the periodic table.

Calculating Empirical Formula from Percentage Composition

The same method is used to calculate empirical formula from mass data.
Treat percentages as if they were masses, and use the atomic mass of the element (A) from the periodic table to convert the mass into moles.

Calculating Empirical Formula from Combustion Data

Several steps are required here, starting with determining the masses of carbon (C) and hydrogen (H) in the compound (from the mass of combustion products). After calculating moles of C and H, determine the elements ratio (e.g., 1 C : 2H) to find the empirical formula

Moles and Equations

Understanding how to write formulae and balance chemical equations.
In general, a balanced chemical equation shows the same number of each type of atom on both sides.
Write names of the reactions then use their chemical formula to solve the calculations.
Use atomic masses on the periodic table to find the quantity of the substance/reaction.
Use the mole ratio together with the information provided in the question to obtain the quantity/volume as required in the question.

Bonding

Atoms gain stability by attaining a complete outer shell of electrons, which is often achieved by losing or gaining electrons to form ions, or sharing electrons with other atoms.

Intramolecular Bonding

Ionic bonding occurs when one atom gains one or more electrons and another loses one or more electrons to gain stability.
Covalent bonding occurs when atoms share one or more pairs of valence electrons to achieve stability.
Metallic bonding occurs when atoms lose their valence electrons, forming a 'sea' of electrons that attract the positive metal ions, causing a solid.
Dative covalent/coordinate bonding is a special type of covalent bonding where both electrons in the shared pair bonding comes from the same atom.

Intermolecular forces

Permanent dipole-dipole attraction occurs when polar molecules, where one side is positively charged and the other is negatively charged, are attracted to each other.
Hydrogen bonding is a special type of permanent dipole-dipole attraction that occurs when hydrogen is bonded to a highly electronegative atom (O, N or F).
Temporary dipoles/Van der Waals forces exists due to electron movement on the atoms involved and results in a weak attraction between atoms/molecules.

Other

Learn the common chemical formula, or use the periodic table to deduce the formula given by the name
When writing reactions use the correct state symbols for each substance to describe whether it is solid, liquid, aqueous, gas or aqueous (s),(l),(g),(aq)

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Description

This quiz covers key concepts in chemistry regarding ionic equations, moles, and the behavior of compounds in solutions. Questions include identifying spectator ions and understanding the implications of heating certain compounds. Test your knowledge on stoichiometry and chemical reactions.