1.3 Chemical calculations

Define relative atomic mass

the average mass of one atom of the element relative to 1/12 the mass of one atom of carbon-12.

define relative isotopic mass 

the mass of an atom of an isotope relative to 1/12 the mass of an atom of carbon-12.

define relative formula mass.

the average mass of a molecule relative to 1/12 the mass of an atom of carbon-12.

What is vaporisation in a mass spectrometer?

the sample is heated and turned into a gas before it enters the spectrometer.

What is ionisation in a mass spectrometer?

the gaseous sample is bombarded with high energy electrons from an electron gun. This knocks electrons off the particles to form positive ions.

What is acceleration in a mass spectrometer?

the positive ions are accelerated using an electric field and a vacuum pump.

What is deflection in a mass spectrometer?

the ions are deflected by a magnetic field. The amount of deflection depends on the mass and charge of the ion. Lighter ions are deflected more than the heavier ones. (Lighter ions are deflected more than heavier ones)

What is detection in a mass spectrometer?

some ions pass through a slit and are detected by the detector . Only those ions with the correct mass/charge ratio will be able to pass through the slit.

Why does the inside of the spectrometer have a vacuum?

so that air molecules do not interfere with the movement of the ions.

Whats the equation fir moles calculations with a mass?

Mass (g) = moles x Mr

Whats the ideal mass equation?

PV= nRT

P = pressure (Pascals pr Nm-²)

V = Volume (m³)

n= moles

R = Gas constant (always in question)

T = temperature (always in Kelvin )

Whats the equation involving the changes in condition?

First PxV / T = second PxV / T

How do we figure out the concentration with moles? (Mol/dm³)

Concentration = moles / volume in dm³

How do u convert cm³ to dm³

Divide by 1000

Whats the equation for atom economy?

(Mass of require product / total mass of reactant ) x 100

Whats the equation for percentage yield?

(Mass of product obtained / theoretical mass ) x 100

Whats the percentage error for a 25cm ³ pipette?

0.06cm³

Whats the percentage error on a 50cm³ burette?

0.1 cm³

Whats the percentage error on a 250cm³ flask?

0.2cm³

Whats the percentage error on a balance?

0.01g

How to calculate percentage error?

( Percentage error / value measured ) x100