Topic 2 Flashcards
which of the following substances will be a solid at 20 degrees and will melt when placed in a beaker of hot water at 80 degrees?
A) MP - 122 , BP - 249
B) MP - -7, BP - 59
C) MP - 30, BP - 2403
D) MP - -32, BP - 27
C
a student set up the apparatus shown to obtain pure water from sea water by distillation
explain how the water in sea water separates to produce the pure water in this apparatus
water boils to form steam and this steam condenses to form pure water
a student set up the apparatus shown to obtain pure water from sea water by distillation
explain how the apparatus could be improved to increase the amount of pure water collected from the same volume of sea water
use a condenser (surrounds test tube with cold water) to increase effectiveness of cooling
a substance is heated at a constant rate and its temperature is taken every minute. during the heating, the substance undergoes one change in state.
explain the shape of the graph in terms of the changes in movement and arrangement of the particles as the substance is heated.
(graph shows room A-B increasing then stops at B-C and increases more after C)
from a-b the graph rises because in a solid particles are in a fixed lattice so they vibrate quicker as temperature increases.
from b-c the graph is flat because particles in a solid use energy to break intermolecular bonds to turn from a solid to a liquid.
from c-d the graph rises because particles in a liquid move past one another and move more rapidly as temperature increases
in a different method of obtaining nickel, the process produces a mixture of the liquids nickel tetracarbonyl and iron pentacarbonyl.
the boiling point of nickel tetracarbonyl is 43 degrees
the boiling point of iron pentacarbonyl is 103 degrees
these two liquids mix together completely.
describe the process used to separate these two liquids
use fractional distillation to heat the mixture. nickel will boil first as it has a lower boiling point so will boil first
a sample of rock salt contains a mixture of sodium chloride and some insoluble substances. the rock salt is added to water and the mixture stirred. the mixture is then filtered to obtain a filtrate of sodium chloride solution.
describe how a sample of pure, dry sodium chloride crystals can be obtained from the filtrate
first heat the solution then leave the solution to crystallise and scrape crystals from container and pat dry between filter papers
inks contain coloured dyes. samples of four inks, W, X, Y and Z were separated using paper chromotography. (photo shows diagram)
in the experiment the solvent front moved 6.5cm. calculate the rf value of the dye that is present in both inks X and Z
Rf = 0.6
inks contain coloured dyes. samples of four inks, W, X, Y and Z were separated using paper chromotography. (photo shows diagram)
state what could be changed in the experiment to make the Rf value more accurate
longer paper
inks contain coloured dyes. samples of four inks, W, X, Y and Z were separated using paper chromotography. (photo shows diagram)
in this experiment, ink sample Y did not move from the start line. explain a change to the experiment that would be needed to separate the dyes in ink sample Y
use a different solvent so the ink will dissolve
