12.5. Identification of ions and gases
A subsection of Chemistry, 0620, through 12. Experimental techniques and chemical analysis
Listing 10 of 359 questions
The table shows the ions present in a 1000 cm3 sample of blood plasma. ion present formula of ion mass present in the 1000 cm3 sample / g sodium Na+ 3.25 potassium K+ 0.16 calcium Ca2+ 0.10 magnesium Mg2+ 0.04 chloride Cl – 3.65 hydrogencarbonate HCO3 – 1.50 phosphate PO4 3– 0.64 sulfate SO4 2– 0.10 Answer these questions using only information from the table. Which positive ion is present in the lowest concentration? Give the name of the compound formed from K+ and Cl – ions. Calculate the mass of potassium ions present in 200 cm3 of this blood plasma.  mass of potassium ions = g When the 1000 cm3 sample of blood plasma is crystallised, several compounds are formed. Suggest the name of the compound which forms the greatest mass of crystals. Describe a test for potassium ions. test result  Blood plasma also contains proteins. Proteins are present in food. Which one of the following substances is also present in food? Draw a circle around the correct answer. carbohydrate hematite polyterylene  CompoundS is one of the monomer units used to make proteins. Its structure is shown. H2N CH compound S CH2 COOH OH On the structure, draw a circle around the alcohol functional group. Deduce the molecular formula of compoundS showing the number of carbon, hydrogen, oxygen and nitrogen atoms. 
0620_w18_qp_31
THEORY
2018
Paper 3, Variant 1
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The table shows the concentrations of the ions present in a solution obtained from cells in the body. ion present formula of ion concentration in mg / 1000 cm3 sodium Na+ potassium K+ calcium Ca2+ magnesium Mg2+ chloride Cl – hydrogencarbonate HCO3 – phosphate PO4 3– Answer these questions using only information from the table. Which negative ion is present in the highest concentration? Calculate the mass of potassium ions present in 250 cm3 of this solution.  mass of potassium ions = mg Calculate the total mass of positive ions present in 1000 cm3 of this solution.  total mass of positive ions = mg Give the name of the compound formed from Na+ and HCO3 – ions. Describe what is observed in these two reactions. ● ● An excess of aqueous sodium hydroxide is added to a solution containing Ca2+ ions. ● ● An excess of aqueous ammonia is added to a solution containing Ca2+ ions.  Lacticacid can build up in muscle cells during exercise. The structure of lacticacid is shown. C COOH OH H CH3 On the structure, draw a circle around the carboxylic acid functional group. Deduce the molecular formula of lacticacid showing the number of carbon, hydrogen and oxygen atoms. Lacticacid can form a polymer. Complete the sentence about polymers using words from the list. atomic large molecular monomers polymers small During polymerisation molecules called join together to form long-chain molecules with a very high relative mass.  
0620_w18_qp_32
THEORY
2018
Paper 3, Variant 2
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The diagrams show the structures of four substances, R, S, T and U. R T U S C C C H H H H H H C C H H H H C C H H H H C C H H H H C C H H H H O C O O C O O C O O C O Ti Ti Ti Ti Ti Ti Ti Ti Ti Ti Ti NH4 + NH4 + Cl – NH4 + NH4 + Cl – NH4 + Cl – Cl – State which one of these substances, R, S, T or U: is an element contains ionic bonds is a gas at room temperature is a polymer. Ammonium chloride is present in some fertilisers. Which two of the following compounds are also present in many fertilisers? Tick two boxes. hydrogen sulfide calcium phosphate copper(fluoride nickel(oxide potassium nitrate  A mixture of ammoniumchloride and aqueous sodiumhydroxide is heated as shown. heat mixture filter paper soaked in methyl orange and acid The filter paper changes colour from red to yellow. Explain why. 
0620_w18_qp_32
THEORY
2018
Paper 3, Variant 2
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