Chem 6A Midterm 1

Definitons

100

What is an isotope?

Atoms that have a different number of neutrons compared to protons.

200

What is a homogenous mixture? 

A mixture where all individual components are uniformly mixed. 

300

Describe the difference between a law and theory. 

A law is a brief statement that summarizes past observations and predict future ones. A theory is a unifying principle that explains a law, based on experimental observations.

400

What is a solute and a solvent? 

The solute is what is being dissolved, while the solvent is what is dissolving the solute. The solvent is in excess, while the solute is the limiting substance in a solution. 

500

What is a nonelectrolyte, a strong electrolyte, and a weak electrolyte? 

nonelectrolyte: substance that does not conduct electricity, since no ions are present. 

Strong: a substance that is present almost entirely as ions in a solution. 

Weak: incompletely ionized, meaning that most of the compounds have remained intact.

Unit conversions

100

What is 0.000245 g in mg?

0.245 mg

200

What is 0.000127 km in mm?

127 mm

300

What is 1.79 nm in mm?

0.00000179 mm, or 1.79x10^-6 mm

400

What is 356 m to pm?

3.56x10¹⁴ pm

500

There is 5.064 x 10⁶ L of a substance. The
density of this substance is 3.02 g/cm3. What is the mass of the fuel in Mg?

1.53x10⁴ Mg

Elements & Reactions

100

You have 5.30 g of iron (Fe), how many moles do you have?

0.095 mol

200

Balance: KClO₃ → KClO₄ + KCl

4KClO₃ → 3KClO₄ + KCl

300

How many carbon atoms are in 0.850 mol of acetaminophen (C₈H₉NO₂)?

4.09x10²⁴ atoms

400

Write the net ionic equation for the following reaction:

NiCl₃ + K₃PO₄ ---> NiPO₄ + 3KCl

(don't forget the phases)

Ni³⁺(aq) + PO₄^3-(aq) ---> NiPO₄(s)

500

A compound is found to contain 64.80% carbon, 13.62% hydrogen, and 21.58% oxygen by weight. What is the empirical formula for this compound? The molecular weight for this compound is 148.16 g/mol. What is its molecular formula?

Formula: C₄H₁₀O

molecular: C₈H₂₀O₂

nomenclature

100

Classify each compound as ionic or molecular:

 a. Fe₂O₃ b. SO₄ c. H₂O d. NaCl

a) Ionic b) molecular c)molecular d)Ionic

200

Write the formula for: Iron (III) hydroxide

Fe(OH)₃

300

Write the name for: P₂O₅

diphosphorus pentoxide

400

Write the formula for: Ammonium carbonate

(NH₄)₂CO₃

500

Write the name for:

K₂HPO₄

Potassium Hydrogen Phosphate

week 4 worksheet

100

If 92 g of SF₆ is produced from the reaction of 115 g of sulfur in excess fluorine, what is the percentage yield?
S(s) + 3F₂(g) → SF₆(g)

18%

200

What is the minimum volume, in mL, of 1.1 M NaOH that must be reacted with excess chlorine gas to yield 2.2 grams of sodium hypochlorite?
2NaOH + Cl₂ --> NaOCl + NaCl + H₂O

54 mL

300

How many grams of nitrogen gas form when 100 g
N₂H₄ and 200 g N₂O₄ are mixed? Identify the limiting and excess reagents.

2N₂H₄ + N₂O₄ --> 3N₂ + 4H₂O

131 g N₂

Limiting= N₂H₄

Excess= N₂O₄

400

What mass (in g) of C₃N₃(NH₂)₃ will be obtained from
190.0 kg of HNCO if the overall reaction has an 82.0% yield?

6HNCO --> C₃N₃(NH₂)₃ + 3CO₂

7.61x10⁴ g of C₃N₃(NH₂)₃

500

The combustion of an unknown hydrocarbon produced 8.8 g of CO₂ and 4.5 g of H₂O. The molar mass of the
compound it 58.124 g/mol. What is the molecular formula of the compound?

C₄H₁₀