Chemistry Unit Conversions

Find heat energy (define symbols and letters)

q=CmΔT

heat energy = specific heat cap x mass x temp change

q = heat energy in J, C is specific heat capactiy (J g-10 C), m is mass in grams and ΔT is temp change

How to find pH

pH = -log10(H30+)

10^-14=?

[H30][OH-] = 10^-15

mass-mass stoich

m/M= n → n(find) → m=n xM

solution solution stoich

n=cv n(given)→n(find), c=n/v

Outline Graviemetric analysis (which calc., what is it and errors)

To find the concentration of an ion in a sample of solution, precipitate the ion out by adding another substance. Get the dried weight of the precipitate and given the molar mass of the known precipitate find the number of moles of precipitate as step 1 of a stoichiometry problem.
known chemical formula, be pure and be stable.
•
• Procedure uses mass-mass stoichiometry calculations
• Relies on the formation of a precipitate as a result of the addition of another
reagent. The precipitate is filtered, washed, dried and weighed. Using the %
composition of the analyte, the concentration of the product is used to infer the
concentration of the element in the original solution
• Error in the procedures include failing to fully precipitate the analyte, failing to
wash the filtrate thoroughly, loss of filtrate through dissolving in the washing
solution, inadequate drying of the filtrate. Also measurement error using the
scales to weigh the filtrate by difference

spectroscopic analysis

Spectroscopic Analysis:  To find the concentration of an ion in a sample of solution, You need a set of solutions created by diluting a standard. These are run through a UV-VIS spectroscope or a colorimeter and the absorbance is plotted against the concentration.  This should be a linear graph due to Beers Law - the absorbance increases with increasing concentration.

• You need to know: the difference between the two spectroscopies studied

  UV-Vis spectroscopy covers a broader range of wavelengths and is more quantitative, whereas colorimetry is specifically focused on the visible spectrum and is often more subjective

• You need to know: how to plot a calibration curve

• You need to know: how to ACCURATELY read a value from the curve

• You need to know: limitations and sources of error in the method

• You need to know: how to account for any dilution

Outline Spectroscopy

Wavelengths of light in the UV and visible part of the EMR spectrum
is absorbed by a coloured solution. The absorbance of a set of
standard solutions is measured under the same conditions as a
sample. Solutions absorb their complementary colours of light

Volumetric Analysis

o find the concentration of an acid or a base you must neutralise it using a standard. Volumtric glassware is used. The concentration is determined using stoichiometry.

• You need to know: How to make a standard solution, the properties of primary standards and how to do the calculation of the concentration of a standard: use anhydrous soluble compound of known mass (measure) and filter it into a volumetric flask, fill it up to the line using the pipette

• You need to know: how to do volume-volume stoichiometry

• You need to know: unit conversions

• You need to know: the steps in the method

• You need to know: sources of error and their impact on the product formed: parallax error and end point as colour change is objective.

kpa to atm and atm to kpa

KPA→ ATM divide by 101.3

ATM→KPA multiply by 101.3

g/L. mol/L. mg/mL, ppm, %m/m, %v/v, %m/v