Chemical Reactions

When a candle burns, the mass of the candle decreases. Why does this NOT violate the Law of Conservation of Mass?

How many hydrogen atoms are in the formula $(NH_4)_2SO_4$?

What is the main difference between a word equation and a chemical formula equation?

Which of these is NOT a reactant in the word equation: $Hydrochloric\ acid + Sodium\ hydroxide \\rightarrow Sodium\ chloride + Water$?

What is the coefficient of $H_2O$ in the balanced equation: $2H_2 + O_2 \rightarrow \dots H_2O$?

Which equation is correctly balanced for the reaction of iron(III) oxide with carbon monoxide?

Identify the reactants in the following equation: $CuSO_4 + Zn \rightarrow ZnSO_4 + Cu$.

Phosphorus pentachloride reacts with excess water to form phosphoric acid and hydrogen chloride. What is the sum of the coefficients of the products?

Arsenic(III) oxide reacts with water to form arsenous acid: $As_4O_6 + H_2O \rightarrow H_3AsO_3$. What is the coefficient of $H_3AsO_3$ when balanced?

The dehydration of copper(II) sulfate pentahydrate is $CuSO_4 \cdot 5H_2O \rightarrow CuSO_4 + 5H_2O$. How many molecules of water are released for every formula unit of the hydrate?

In the equation $2Na + 2H_{2}O \rightarrow 2NaOH + H_{2}$, how many hydrogen atoms are on the product side?

How many carbon atoms are in $3CO_{2}$?

What coefficient is needed to balance $2HgO \rightarrow xHg + O_{2}$?

In the formula $2Mg(OH)_{2}$, how many oxygen atoms are present?

In the reaction between barium hydroxide and phosphoric acid, $Ba(OH)_2 + H_3PO_4 \rightarrow Ba_3(PO_4)_2 + H_2O$, what is the coefficient for $H_2O$?

What is the sum of coefficients for the reaction $H_3PO_4 + 3KOH \rightarrow K_3PO_4 + 3H_2O$?

Balance the synthesis of sulfur trioxide from sulfur dioxide: $SO_2 + O_2 \rightarrow SO_3$. What is the coefficient for $SO_2$?

If a reaction follows the pathway shown, and the total mass of A and B is 50g, what is the mass of C?

Consider the unbalanced equation $C_6H_6 + O_2 \rightarrow CO_2 + H_2O$. What is the coefficient of $O_2$ in the simplest whole-number balanced form?

When balancing the equation $Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$, what is the total number of oxygen atoms on the product side?

Which of these equations is NOT a synthesis reaction?

When energy in the form of electricity is used to break down a compound, the process is often a type of:

In the reaction $C_{2}H_{5}OH + 3O_{2} \rightarrow 2CO_{2} + 3H_{2}O$, which substance is the fuel?

Identify the type of reaction: $4Fe + 3O_{2} \rightarrow 2Fe_{2}O_{3}$

What is the primary reason that thermal decomposition reactions usually require a constant input of heat?

Which type of reaction is the following: $2K + Br_{2} \rightarrow 2KBr$?

Complete combustion of a fuel is more efficient than incomplete combustion because:

Synthesis of a metal hydride occurs when a metal reacts with hydrogen gas. If $2$ moles of Sodium react with $1$ mole of $H_{2}$, what is the formula of the product?

A hydrocarbon with the formula $C_{2}H_{2}$ (ethyne) undergoes complete combustion. What is the ratio of the volume of $CO_{2}$ produced to the volume of $O_{2}$ consumed (at constant $T, P$)?

The photolysis of silver chloride ($AgCl$) in sunlight is an example of which reaction type?

A catalyst works by:

If a reaction rate is $0.2 g/s$, how many grams of reactant are consumed in 60 seconds?

To ensure a fair test when investigating the effect of surface area on reaction rate, what should be kept constant?

Why does increasing the temperature of a reaction have such a large effect on the rate?

A student performs two trials of a reaction between magnesium ribbon and hydrochloric acid to produce hydrogen gas. In both trials, $0.1\text{ g}$ of magnesium ribbon is the limiting reactant.

Trial 1: $25\text{ cm}^{3}$ of $2.0\text{ mol/dm}^{3}$ HCl is used. Trial 2: Distilled water is added to the acid to create $50\text{ cm}^{3}$ of $1.0\text{ mol/dm}^{3}$ HCl.

Which statement correctly describes the observations in Trial 2 compared to Trial 1?

Which of the following represents the correct sequence of events when a catalyst is used?

Why is the initial rate of a reaction the most commonly used value for comparison?

How does the distribution of kinetic energy in a liquid sample compare to a gas sample at the same temperature?

Which factor affects the rate of a chemical reaction but NOT the value of the rate constant $k$?

In a turbidity experiment (the 'disappearing cross' experiment), the rate is often expressed as $1/time$. What is the underlying assumption of this method?

Which factor is primarily changed when we increase the pressure of a gas?

If a reaction occurs very slowly, it means that:

Which of these changes will NOT increase the collision frequency?

What does the $E_a$ symbol stand for in chemistry?

Which of the following relates temperature to the energy of particles?

If you have two identical reactions, but one uses a catalyst, which reaction will have the same final amount of product (assuming reactants are the same)?

Why does 'clumping' of solid reactants slow down a reaction?

A chemical engineer is studying the reaction $A(g) + B(g) \rightarrow C(g)$. They are tasked with increasing the rate of product formation while ensuring that the total number of initial collisions per second (represented by Node N1 in the flowchart) remains constant to avoid an unstable pressure buildup. Based on collision theory, which intervention should be chosen and which node's requirement is being modified?

According to collision theory, why are most collisions between molecules unsuccessful?

What is the effect of adding an inhibitor to a chemical reaction?

What happens to the white anhydrous copper(II) sulfate if it is left in a damp room?

Which of the following is a key feature of dynamic equilibrium?

If a reaction is 'endothermic' in the forward direction, what happens if we add heat?

Why does adding more reactant usually result in more product in a reversible system?

How does the addition of a catalyst affect the yield of a product in a reversible reaction?

Why is the equilibrium state described as 'macroscopically static'?

In the equilibrium $CO(g) + 2H_{2}(g) \rightleftharpoons CH_{3}OH(g)$, what happens to the yield of $CH_{3}OH$ if the pressure is increased?

For a particular reversible reaction, the activation energy of the forward reaction is $150 kJ/mol$ and that of the reverse reaction is $120 kJ/mol$. Which of the following is true?

In the equilibrium $N_{2}O_{4}(g) \rightleftharpoons 2NO_{2}(g)$, if the total pressure is increased by decreasing the volume, what happens to the mole fraction of $NO_{2}$?

Which of the following describes the behavior of a system where the rate of the forward reaction is greater than the rate of the reverse reaction?