Chem exam 1 review

Definitions

100

Define science and the science of chemistry. 

Explain how do we do science. 

Science: systematic endeavor to understand a natural phenomenon 

Chemistry: scientific study of matter and its' transformations

We do science through experiments! Science experiments must be objective (without bias). In order to be objective the data must be reproducible and verifiable. 

200

Describe two types of data

1.) Qualitative 

data involving senses (ex: smell, taste, etc.)

2.) Quantitative 

data involving numbers (ex: heart rate, pulse, etc.)

300

What are transformations? What types are there? What makes transformations happen? 

transformations: what is happening and why is it happening?

2 types: physical (ex: changes in state) and chemical (wood burning)

Energy makes transformations happen

400

define atomic mass

weighted average of all naturally occurring isotopes of an element

(different than mass #)

500

What are the mass laws?

1.) conservation of mass: mass is neither created nor destroyed during a reaction 

2.) definite proportions: for a given compound the ratio of components is fixed. If the ratio changes the compound changes

3.) multiple proportions: when 2 elements form a compound this will always be in whole number ratios

Practice problems 1

100

Compound 1 is found to have 14g N for every 16g O. Compound 2 is found to have 28g N for every 16g of O. Prove mass law number 3. 

You will get a whole number ratio of two which proves mass law three. 

200

Find the number of O atoms in 12.456 grams of NO_2. 

3.261 x 10²³  O atoms 

300

a compound containing Na, Cl, and O is analyzed and it is found it has 2.82 g Na, 4.35 g Cl, and 7.83 g O. What's the empirical formula? 

NaClO₄

400

medical experts generally believe a level of 30 micrograms Pb per deciliter of blood poses significant health risk. Express this is a.) the unit mol Pb/L blood; b.) as the # of Pb atoms per milliliter of blood. 

a.) 1 x 10^-6  mol/L

b.) 6.022 x 10¹⁴ atoms

500

Solid lithium hydroxide is used in space vehicles to remove exhaled carbon dioxide from the living environment by forming solid lithium carbonate and water. What mass of gaseous carbon dioxide can be absorbed by 1.00 kg of lithium hydroxide? 

919 grams

Practice problems 2

100

Find number of protons, neutrons, and electrons for ⁴⁰Ca²⁺. 

protons: 20 

neutrons: 20

electrons: 18

200

What's the mass percent of O in NO₃?

77.4%

300

How many ²⁰⁴Pb atoms are present in a piece of lead weighing 215 mg. (The natural percent abundance of ²⁰⁴Pb is 1.4%).

8.7 x 10¹⁸ atoms 

400

A compound contains 47.08% carbon, 6.59% hydrogen, and 46.33% chlorine by mass. Molar mass of the compound is 153 g/mol. a.) find empirical formula. b.) find molecular formula

a.) C₃H₅Cl

b.) C₆H₁₀Cl₂

500

In the course of the combustion analysis of an unknown compound containing only carbon, hydrogen, and nitrogen, 12.923 g of carbon dioxide and 6.608 g of water were measured. Treatment of the nitrogen with H2 gas resulted in 2.501 g NH3. The complete combustion of 11.014 g of the compound needed 10.573 g of oxygen. What the compound’s empirical formula?

C₂H₅N

Sig Figs

100

All _________ are always significant.

non-zero numbers (1-9)

200

Zeros before all non-zero digits are _______. Zeros between 2 non-zero digits are ________. 

never significant 

always significant

300

How many sig figs are in 100.0?

4 sig figs

400

How many sig figs are in 0.0007?

1 sig fig

500

How many sig figs are in 33.303?

5 sig figs. 

Nomenclature

100

potassium sulfide

K₂S

200

iron (II) chloride

FeCl₂

300

V₂O₅

vanadium (V) oxide

400

CuSO₄ 6H₂O

copper (II) sulfate hexahydrate

500

Name the acids: 

 1.) phosphoric acid

2.) hydrobromic acid 

3.) nitric acid

4.) hydroiodic acid

1.) H₃PO₄

2.)HBr

3.) HNO₃

4.)HI