Unit 4 Test Review: Conservation of Matter, Reactions, and Stoichiometry

Comprehensive practice flashcards covering Unit 4 topics including the Law of Conservation of Mass, reaction types, counting atoms, the Law of Definite Proportions, molar mass, and balancing chemical equations.

True or False: Conservation of mass states that matter cannot be created or destroyed during a chemical reaction.

True

Based on the Law of Conservation of mass, if a reaction starts with $32.8\,g$ of a substance, what will the mass of the product be?

$$32.8\,g$$

In the reaction $\text{Magnesium} + \text{Oxygen} \rightarrow \text{Magnesium Oxide}$, how much magnesium is needed to react with $12\,g$ of oxygen to produce $32.5\,g$ of magnesium oxide?

$$20.5\,g$$

In the complete reaction of $35.52\,g$ of sodium with $26.86\,g$ of chloride, what mass of sodium chloride is formed?

$$62.38\,g$$

If an experiment is done in an open system, why would there be a change in mass for the products?

Mass can be lost or gained to the surroundings

What type of chemical reaction is $2HgO \rightarrow 2Hg + O_2$?

Decomposition

True or False: Formation of a gas is evidence that a chemical reaction has occurred.

True

On which side of a chemical reaction equation are the products written (Left or Right)?

Right

What type of reaction is $C_3H_8 + O_2 \rightarrow CO_2 + H_2O$?

Combustion

How many atoms of oxygen are present in the compound $2Ca_3(PO_4)_2$?

$$16$$

How many atoms of hydrogen are present in $2CH_4$?

$$8$$

How many carbon atoms are in the compound $2C_6H_{12}O_6$?

$$12$$

In a carbon dioxide molecule there will always be $1$ carbon atom for every $2$ oxygen atoms. What law is this?

The Law of Definite Proportions

What is Avogadro's number?

$$6.022 \times 10^{23}$$

What is the molar mass of $MgCl_2$?

$$95.21\,g\,mol^{-1}$$

What is the molar mass of $CaCl_2$?

$$95.45\,g\,mol^{-1}$$

True or False: When balancing a chemical equation, the only number you should change to make the elements balance is the coefficient.

True

Balance the chemical equation: $\text{\_\_\_ } Zn + \text{\_\_\_ } HCl \rightarrow \text{\_\_\_ } ZnCl_2 + \text{\_\_\_ } H_2$

$$Zn + 2HCl \rightarrow ZnCl_2 + H_2$$

Balance the chemical equation: $\text{\_\_\_ } P + \text{\_\_\_ } Cl_2 \rightarrow PCl_3$

$$2P + 3Cl_2 \rightarrow 2PCl_3$$

Balance the chemical equation: $\text{\_\_\_ } H_2 + \text{\_\_\_ } O_2 \rightarrow \text{\_\_\_ } H_2O$

$$2H_2 + O_2 \rightarrow 2H_2O$$