Purity & Separating Mixtures (OCR Gateway GCSE Chemistry: Combined Science)

Which of the following is not a pure substance?

A student was investigating the colours in black food colouring. 

Chromatography was carried out on samples A-E and compared to the black food colouring. 

The following chromatogram was produced. 

Which of the following conclusions is not true for this chromatogram?

A company produces tin from an ore called cassiterite, which is mainly tin oxide.

What is the relative formula mass (M_r) of tin oxide, SnO₂?

Relative atomic masses (A_r):   Sn= 119 O= 16

The diagram shows the displayed formula of succinic acid. 

What is the empirical formula for this compound?

A student set up the following apparatus to investigate the colours in three different food colourings.  

What are the stationary and mobile phases for this experiment? 

A student making copper sulfate crystals used the method below. 

Unreacted copper carbonate was left over as it had been added in excess.

Which separation technique could be used to separate the unreacted copper carbonate and solution into different containers?

A mixture contains methanol and ethanol. They have different boiling points. 

Which method could be used to separate this mixture?

A student carried out chromatography on a sample of green ink. 

The distance moved by the solvent front is 5.8 cm. 

The distance moved by the yellow dye is 4.5 cm.

Calculate the R_f value of the yellow dye to 2 significant figures. 

The diagram below shows a heating curve for a pure substance.

Which part of the curve shows a change of state happening?

The gas chromatogram shows the different substances in a gas mixture. 

Which statement below is not true?