Molecules or ions that contain an element with an oxidation state of +5 include

1 H₂SO₃

2 NO₂⁺

3 [Cr(H₂O)₄Cl₂]⁺

4 ClO₃^-

What is the coefficient for O₂ (g) when the equation below is balanced?

__C₃H₈ (g) + __O₂ (g) → __CO₂ (g) + __H₂O(g)

Which of the physical properties below decrease with increasing atomic number for both the alkali metals and the halogens?

I. Atomic radius

II. Ionization energy

III. Melting point

For the reaction below

H₂ (g) + I₂ (g) → 2HI(g)

at a certain temperature, the equilibrium concentrations are (in mol dm⁻³):

[H₂]=0.30, [I₂]=0.30, [HI] =3.0

What is the value of K?

The following reactions are spontaneous as written.

Fe(s) + Cd²⁺ (aq) → Fe²⁺ (aq) + Cd(s)

Cd(s) + Sn²⁺ (aq) → Cd²⁺ (aq) + Sn(s)

Sn(s) + Pb²⁺ (aq) → Sn²⁺ (aq) + Pb(s)

Which of the following pairs will react spontaneously?

I. Sn(s) + Fe²⁺ (aq)

II. Cd(s) + Pb²⁺ (aq)

III. Fe(s) + Pb²⁺ (aq)

Which of the following factors affect the amount of product formed during electrolysis?

I. The current used

II. The duration of electrolysis

III. The charge on the ion

6.4 g of copper wire is added to 0.10 dm3 of 1.0 moldm⁻³ aqueous AgNO₃ to form metallic silver and aqueous copper(II) nitrate. When the reaction is complete,

The ionisation of sulfuric acid is represented by the equations below:

H₂SO₄ (aq) + H₂O(l) → H₃O⁺(aq) + HSO₄⁻(aq)

HSO₄⁻(aq) + H₂O(l) → H₃O⁺(aq) + SO₄²⁻(aq)

What is the conjugate base of HSO₄⁻ (aq) ?

Which statement about bond enthalpies is correct?

Which molecule has the smallest bond angle?

How do bond length and bond strength change as the number of bonds between two atoms increases?

Which one of the following is the electron arrangement of the strongest reducing agent?

Molecules with a permanent dipole include

1 NH₃

2 PCl₃

3 SCl₂

4 SiCl₄

The percentage by mass of the elements in a compound is

C=72%, H=12%, O=16%.

What is the mole ratio of C : H in the empirical formula of this compound?

Which of the reactions below occur as written?

I. Br₂ +2I⁻ →2Br⁻ +I₂

II. Br₂ +2Cl⁻ →2Br⁻ +Cl₂

Based on electronegativity values, which bond is the most polar?

Which of the quantities in the enthalpy level diagram below is (are) affected by the use of a catalyst?

In the reaction below

N₂(g)+3H₂(g) →2NH₃(g) ∆H =−92kJ

which of the following changes will increase the amount of ammonia at equilibrium?

I. Increasing the pressure

II. Increasing the temperature

III. Adding a catalyst

Which statement about neighbouring members of all homologous series is correct?

Which of the following atoms has/have one or more unpaired electrons?

I. Iron

II. Copper

III. Zinc

In which pair is the first species larger than the second?

The carbon-carbon-carbon bond angle in CH₃CHCH₂ is closest to

The molar mass of an unknown gas is to be determined by weighing a sample. As well as its mass, which of the following must be known?

I. Pressure

II. Temperature

III. Volume

Using the information below:

H₂ (g) + O₂ (g) → H₂O₂ (l) ∆H = −187.6kJ

2H₂ (g) + O₂ (g) → 2H₂O(l) ∆H = −571.6kJ

what is the value of ∆H (in kJ) for the following reaction?

2H₂O₂ (l) → 2H₂O(l) + O₂ (g)