Chemistry Midterm- Multiple choice

Chemistry is the study of

matter and changes it undergoes

Matter

has mass and takes up space

Weight is a measure of the amount of matter and the effect of

gravity

Calculate the weight in Newtons of an object with mass equal to 5.0 x 10 5 g

and the acceleration due to gravity of 98.0 x 10 -1 m/s 2 . Recall Weight

[Newtons] = mass [kg] x acceleration [m/s 2 ]

4,900 Newtons

An example of qualitative data

texture

An example of quantitative data

volume

A tentative explanation of what is observed

hypothesis

In an experiment, the variable the experimenter plans to change

independent variable

An explanation supported by many experiments

theory

Describes a relationship in nature that is supported by many experiments

scientific law

The practical use of scientific information

technology

Which is NOT a base SI unit

Amount of substance - pounds

Which is NOT a unit for volume

kilometer (km)

1 x 10 -3 kg is equal to

1 g

Find the density in units of (g/cm 3 ) of a substance with a mass of 250 mg

occupying a volume of 250 mm 3

1 g/cm³

Find the volume in units of m 3 of a cube with dimensions 1 x 10^2 cm on a side

1 m³

Chemist found that a complex reaction occurred in three steps. The first step

takes 2.5731 x 10^2 s to complete, the second step takes 3.60 x 10 -1 s, and the

third step takes 7.482 x 10 1 s. The total amount of time elapsed during the

3.3249 x 10 2 s (add them all together)

Sodium (Na) reacts with water (H 2 O) to produce a metallic hydroxide (NaOH)

and hydrogen (H2) gas as follows:

2Na (s) + 2H 2 O (l)  2NaOH (aq) + H 2 (g)

For the reaction above, 112.2 grams of Sodium (2Na) combine with 87.8 grams of water

(2H 2 O). What is the total Mass of the reactants and the Mass of Hydrogen gas

mass of reactants is 200 grams; mass of H 2 gas is 5 grams (add water and sodium)

Matter that has uniform and definite composition

none

Identify the heterogeneous mixture

oil and water

Matter that has uniform and unchanging composition

substance

Example of extensive property

mass

Example of intensive property

density

The ability of a substance to combine with or change into one or more other

substances

chemical property

Three states of matter

solid, liquid, gas

Calculate the mass in kilograms of a gold (Au) bar with the following

dimensions: length = 30.5 cm, width 10.15 cm, and height 7.6 cm. The

density of gold (Au) is 19,000 kg/m

44.7 kg

States that mass is neither created nor destroyed during a chemical reaction

law of conservation of mass

Identify three subatomic particles

protons, electrons, neutrons

The number of protons in an atom is referred to as the element’s

atomic number

The atomic number is

equal to number of electrons = protons

Atoms with the same number of protons but different numbers of neutrons

isotope

Mass number is

atomic number + neutrons

Calculate the weighted average atomic mass for chlorine (Cl), where the first

isotope of chlorine has an atomic mass = 34.969 amu and percent abundance

= 75.77% and the second isotope of chlorine has an atomic mass = 36.966

amu and percent abundance = 24.23%

35.453 amu

Reactions that involve an atom of one element changing into an atom of

another element

nuclear reaction

The smallest particle of an element that retains the properties of the element

atom

Form of energy that exhibits wavelike behavior as it travels through space

electromagnetic radiation

Electrons in the outermost orbital

valence electrons

Statement that atoms tend to gain, lose, or share electrons to acquire a full set

of eight valence electrons

octet rule

The modern Periodic Table of Elements arranges the elements in the

following order

increasing atomic mass

Most of the elements in groups 16 – 18 are classified as

nonmetals

The number of electrons in an octet

8

Elements with similar properties

lithium and sodium

A force that holds two atoms together

chemical bond