NCEA Level 2 Chemistry: Structure, Bonding, and Reactivity

Fill-in-the-blank practice flashcards covering NCEA Level 2 Chemistry concepts including Lewis structures, VSEPR molecular shapes, bonding types, thermochemistry, collision theory, equilibrium principles, and acid-base chemistry.

A molecule with $2$ bonding regions and $0$ lone pairs around the central atom adopts a __________ shape with a bond angle of $180^\circ$.

linear

A molecule containing $2$ bonding regions and $1$ lone pair around the central atom exhibits a bent shape with a bond angle of __________.

$$116^\circ$$

A molecule containing $2$ bonding regions and $2$ lone pairs around the central atom exhibits a bent shape with a bond angle of __________.

$$104.5^\circ$$

A molecule with $3$ bonding regions and $0$ lone pairs around the central atom adopts a __________ shape with a bond angle of $120^\circ$.

trigonal planar

A molecule with $3$ bonding regions and $1$ lone pair around the central atom forms a __________ shape with a bond angle of approximately $107^\circ$.

trigonal pyramidal

A molecule with $4$ bonding regions and $0$ lone pairs around the central atom has a tetrahedral shape with a bond angle of __________.

$$109^\circ$$

In molecular geometry, lone pairs repel more strongly than __________ pairs, which changes the bond angles.

bonding

Boron ($B$) is a common exception to the octet rule because it can be stable with only __________ valence electrons around it.

$$6$$

Ionic compounds consist of a giant 3D lattice held by strong electrostatic attractions and only conduct electricity when __________ or dissolved.

molten

Metals conduct electricity and thermal energy because their structure contains __________ electrons that are free to move.

delocalised

Covalent molecular substances generally possess low melting and boiling points because the intermolecular forces between molecules are __________.

weak

In graphite, each carbon atom is bonded to three others in layers, allowing it to conduct electricity due to mobile __________ electrons.

delocalised

Silicon dioxide ($SiO_2$) is an example of a __________ network solid with high melting and boiling points.

covalent

London dispersion forces occur between all molecules, and larger molecules generally experience __________ London dispersion forces.

stronger

Hydrogen bonding is a strong intermolecular attraction that occurs when hydrogen is directly bonded to nitrogen, oxygen, or __________.

fluorine

State changes such as melting, vaporisation, and sublimation absorb heat from the surroundings and are classified as __________ processes.

endothermic

State changes such as freezing, condensation, and deposition release heat into the surroundings and are classified as __________ processes.

exothermic

One mole of any chemical substance contains exactly __________ representative particles.

$$6.02 \times 10^{23}$$

The equation used to calculate the amount of substance in moles ($n$) from mass ($m$) and molar mass ($M$) is __________.

$$n = \frac{m}{M}$$

A covalent bond formed by the unequal sharing of electrons between two atoms is called a __________ covalent bond.

polar

A symmetrical molecule whose individual bond dipoles are equal and point in opposing directions is typically __________ overall.

non-polar

Hydrogen sulfide ($H_2S$) has an asymmetrical bent molecular shape, making it a __________ molecule.

polar

Collision theory states that reacting particles must collide with sufficient energy to overcome the __________ and with the correct orientation.

activation energy

A catalyst increases the rate of both forward and reverse reactions by providing an alternative pathway with a lower __________.

activation energy

Although a catalyst reduces the activation energy of a reaction, it does not alter the overall enthalpy change, __________.

$$\Delta H$$

On the upper reaction profile diagram, line __________ correctly identifies the activation energy of the reaction.

b

In chemical reactions, breaking bonds requires energy, whereas forming new bonds __________ energy.

releases

An exothermic reaction releases energy into its surroundings, meaning its change in enthalpy ($\Delta H$) has a __________ value.

negative

According to Le Chatelier's principle, adding extra reactant to an equilibrium mixture causes the position of equilibrium to shift to the __________.

right

Increasing the total pressure on an equilibrium gaseous system shifts the equilibrium position toward the side with __________ gas molecules.

fewer

In an endothermic forward reaction, increasing the temperature causes the equilibrium position to shift toward the __________.

right

When writing an equilibrium constant expression ($K_c$), pure solids and pure __________ are omitted.

liquids

According to the Brønsted-Lowry definition, an acid acts as a proton donor, while a base acts as a proton __________.

acceptor

A strong acid completely ionises in aqueous solution, whereas a weak acid only __________ ionises.

partially

When a Brønsted-Lowry acid donates a proton ($H^+$), the remaining species forms its conjugate __________.

base

The mathematical equation used to calculate pH from the hydronium ion concentration is __________.

$$pH = -\log[H_3O^+]$$

At $25^\circ C$, the ion product constant for water is given by $K_w = [H_3O^+][OH^-] =$ __________.

$$1.0 \times 10^{-14}$$

In any aqueous solution at $25^\circ C$, the sum of the pH and the pOH is always equal to __________.

$$14$$

The standard neutralisation reaction between an acid and a carbonate produces a salt, water, and __________.

$$CO_2$$

For weak acids, a larger value of the acid dissociation constant ($K_a$) indicates a __________ acid.

stronger