Unit 04: Toxins

A solution is made by completely dissolving a sample of sodium hydrogen carbonate in water. This solution is classified as a

• heterogeneous compound

• heterogeneous mixture

• homogeneous compound

• homogeneous mixture

Answer explanation

"completely dissolved" indicates a homogeneous solution. it is a mixture because two or more compounds are present in varying proportions - sodium hydrogen carbonate (NaHCO3) and water (H2O).

In which sample of matter can the proportion of its components be varied?

• Cl2 (g)

• Br2 (l)

• KCl (s)

• KBr (aq)

Answer explanation

Cl2 (g) is a pure element.

Br2 (l) is a pure element.

KCl (s) is a pure compound.

KBr (aq) is an aqueous solution, meaning it is KBr in water, thus it a mixture.

Only mixtures can have variable proportions of components, therefore KBr (aq) is the correct answer.

Which type of reaction yields a salt and water as the only products?

• combustion

• fermentation

• neutralization

• polymerization

Answer explanation

A neutralization reaction is when an acid and a base react to produce a salt and water.

What is the percent by mass of oxygen in CH3COOH (gram-formula mass = 60. g/mol)?

• 27%

• 32%

• 53%

• 60.%

Answer explanation

What is the percent by mass of oxygen in CH3COOH (gram-formula mass = 60. g/mol)?

% mass = (mass of part / mass of whole) * 100

the total mass of oxygen in CH3COOH is 32 grams.

there are two oxygens.

each oxygen has an atomic mass of 16 amu. therefore, 2 * 16 amu = 32 g.

the gram-formula mass of CH3COOH is 60 g/mol.

therefore,

% mass = (32 g of O / 60 g) * 100

% mass = 53%

According to one acid-base theory

• 
• 
• 
• 

Answer explanation

In the forward reaction, HSO3- is the reactant and one of the products is SO3 2-.

This means that HSO3- decomposed into H+ and SO3 2-. HSO3- donated the H+ to H2O, which accepted the H+ and became hydronium, H3O+.

According to the Bronsted-Lowry Theory, Bases accept, acids donate.

H2O accepted the H+, therefore H2O acts as a base in this reaction.

HSO3- donated the H+, therefore HSO3- is an acid in this reaction.

Identify the positive ion in the sample of HCl (aq) solution.

Answer explanation

NO CREDIT for H or H2.

Based on Table M, state the color of litmus when placed in a sample of the original HCl (aq) solution.

Using the titration data, determine the concentration of the HCl (aq) solution.

Answer explanation

Use the titration equation.

(Ma)(Va) = (Mb)(Vb)

HCl is the acid. NaOH is the base. (Use Table K and Table L.)

Ma = molarity of the acid

Va = volume of the acid, 15 mL

Mb = molarity of the base, 0.010 M

Vb = volume of the base, 30 mL

Substitute and solve for Ma.

Which phrase describes the composition of a compound?

• different elements physically combined

• different elements chemically combined

• the same element physically combined

• the same element chemically combined

Tags

NGSS.MS-PS1-1

Which phrase describes a sample of NaCl (s)?

• a mixture that has constant composition and

  properties throughout

• a mixture that varies in both composition and

  properties

• a substance that has constant composition

  and properties throughout

• a substance that varies in both composition

  and properties