Chapter 1 Measurements

Some important units of measurement 1-1 .

SI units

(

Le S ystème I nternational d'Unités

): •

I nternational S ystem of Units ( 국제단위계 )

• 1960 년 제 11 차 국제도량형총회 (CGPM,

C onférence G énérale des P oids et M esures

) 에서 명칭과 약칭 "SI" 를 채택 결정 •

7 개의 기본 물리량

, 이름 , 기호 선정

Using prefixes as multipliers

Rather than using exponential notation, we often use prefixes from Table 1-3 to express large or small quantities.

Converting between units

Although SI is the internationally accepted system of measurement in science, other units are encountered. Useful conversion factors are found in table 1-4.

1-2

.

chemical concentrations

1. The mole ▶ ▶ ▶

약자는 화학종이 아보가드로수 몰질량 mol 임 (6.022 Х 10 (molar mass,

M

) 은 화학종 23 개 ) 만큼 있으면 1mol 의 질량 ( 단위 1mol , g)

n

x : X 의 몰수 (mol),

M

x : X 의 몰질량 (g/mol) mass x : X 의 질량 (g)

▶

X 의 밀리몰수 (mmoles)

▶

X 의 몰수 (moles)

Ex) 분자의 몰질량 (

M

) 계산 : 원자질량을 모두 합한 다음 Formaldehyde(CH 2 O) 및 g 을 붙임 .

glucose(C 6 H 12 O 6 ) 의 몰질량 ?

Solutions and their concentrations Molar concentration (c, molarity): 단위 (M, mol/L)

■

Analytical molarity ( 분석몰농도 , mol/L)

■

Equilibrium molarity ( 평형몰농도 , mol/L) (at equilibrium )

▶ [ ]

기호를 사용하여 표시하기도 함

Percent concentration (%) Solution = solute + solvent

Parts per million (ppm) and parts per billion (ppb)

Parts per million parts billion

Sometimes, composition is expressed as

parts per million

(ppm) or

parts per billion

(ppb), which mean grams of substance per million or billion grams of total solution or mixture.

1-3

preparing solutions

To prepare a solution with a desired molarity from a pure solid or liquid, we weigh out the correct mass of reagent and dissolve it in a volumetric flask ( figure 1-3)

Solution-diluent volume ratios

( 용액 묽힘 부피비 ) 진한용액의 부피 : 묽히는 용액의 부피 = A : B

⇒

1 : 4 HCl 용액 = 진한 HCl 부피 1 + 4 부피의 물

p-function

Stoichiometric calculations 2 mol 1 mol 1 mol 2 mol

⇒

양론계수가 맞추어진 화학방정식은 반응물과 생성물의 몰비에 대한 정보를 제공

1-4 Stoichiometry calculations for Gravimetric Analysis

Chemical analysis based on weighing a final product is called

gravimetric analysis

.

1-5 . introduction to titrations

Procedures in which we measure the volume of reagent needed to react with

analyte

(the sub-stance being measured) are called

volumetric analysis.