Review for Science Assessment III.2 - 10°

Review for Science Assessment III.2

10 ° - 2020

What is a chemical reaction?

It is process in which one or more substances (reactants), are converted to one or more different substances (products).

Types of chemical reactions

• Synthesis: Two or more reactants form one product.r

• Decomposition: A single compound breaks down into two or more simpler substances

• Single-replacement: a more active element displaces (kicks out) another less active element from a compound.

• Double-replacement: two species (normally ions) are displaced

Multiple Choice

The balanced chemical equation 4 Mn + 3 O₂ → 2 Mn₂O₃ is classified as a ___ reaction.

• Synthesis

• Decomposition

• Single-replacement

• Double-replacement

Chemical equation

A chemical reaction is typically represented by a chemical equation, which represents the change from reactants to products.

To write an accurate chemical equation, two things must occur:

• Each product and reactant must be written using its chemical formula (SnO₂).

• The number of atoms of each element must be equal on both sides of the equation. Coefficients are used in front of the chemical formulas in order to help balance the number of atoms.

Multiple Choice

In any chemical reaction, what quantities are always preserved?

• The number of moles and the volumes.

• The number of molecules and the volumes.

• The mass and the number of atoms.

• The mass and the moles.

How to balance chemical equations?

• Balance the metals.

• Balance nonmetals (except H and O).

• Balance hydrogen then oxygen.

Multiple Choice

What are the coefficients that will balance the equation: Fe + O₂ → Fe₂O₃?

• 2, 3, 2

• 1, 3, 2

• 4, 3, 2

• 1, 1, 1, 1

4 Fe + 3 O₂ → 2 Fe₂O₃?

4 mol Fe + 3 mol O₂ produce 2 mol Fe₂O₃

4 atoms Fe + 3 molecules O₂ produce 2 molecules Fe₂O₃

Measuring Mass in Chemistry

Molar Mass

The molar mass is the mass of a given chemical element or chemical compound (g) divided by the amount of substance (mol).

Multiple Choice

What is the mass in grams of 2.00 moles of water?

• 18.0 grams H₂O

• 36.0 grams H₂O

• 9.01 grams H₂O

• 72.0 grams H₂O

Percent Composition

Multiple Choice

What is the empirical formula of a compound that is 85.7% carbon (C) and 14.3% hydrogen (H) by mass? Use the format CxHy, for example C₆H₁₂

• C₂H₄

• C₃H₁₀

• C₂H₉

• CH₄

Avogadro’s Hypothesis

At STP, 1 mol, or 6.02 × 10²³ representative particles, of any gas occupies a volume of 22.4 L.

The quantity, 22.4 L, is called the molar volume of a gas.

Multiple Choice

If the density of an unknown gas Y is 2.50 g/L at STP, what is the molar mass of gas Y?

• 56.0 g/mol

• 0.11 g/mol

• 22.4 g/mol

• 0.0446 g/mol