C2.3 Flashcards

Questão	Responda
Why do we count only protons and neutrons to calculate the mass number of an atom?	The mass of an electron is very small compared to that of a proton or neutron
How many protons, electrons and neutrons are there in an atom of 19/9F? 19=mass number 9=atomic number	9 protons, 9 electrons, 10 neutrons
What are isotopes?	Atoms of the same element or atoms with the same atomic/proton number that have different numbers of neutrons
What is the mass of one mole of sodium atoms?	23g
Why is the relative atomic mass of chlorine not a whole number?	It has (two main) isotopes and the relative atomic mass is an average value
Calculate the relative formula mass (Mr) of sodium sulphate, Na2SO4' (Relative atomic masses: Na = 23, S = 32, O=16)	(23 X 2) + 32 + (16 X4) =142
What is the mass of one mole of magnesium carbonate, MgCO3? (Relative atomic masses: Mg = 24, C = 12, O = 16)	24 + 12 + (16 X 3) = 84g (must have g)
What is the percentage of carbon in methane, CH4? (A, of C =12, Ar of H =1)	(12/16) X 100 =75%
What is the empirical formula of the compound that contains 70% iron and 30% oxygen? (Ar of Fe = 56, Ar of 0 = 16)	70/56=1.25 : 30/16 = 1.875, 1:1.5, 2:3, empirical formula Fe2O3
Calculate the mass of calcium oxide that can be made from 10g of calcium carbonate in the reaction: CaCO3 -> CaO + CO2 (Ar of Ca =40, Ar of O =16, Ar of C =12)	CaCO3 = 100, CaO = 56, one mole CaCO3 gives one mole of CaO or 100g CaCO3 gives 56g CaO, 10g CaCO3 gives (10/100) X 56 == 5.6g
A student made 4.4g of calcium oxide from 4.0g of calcium. Calculate the percentage yield	2Ca + O2 -> 2CaO, 80g Ca ->112g CaO, 4g Ca ->5.6g CaO, (4.4/5.6) X100 = 78.6%
Why is it not usually possible to get 100% yield from a chemical reaction?	Reactions may not go to completion, other reactions may happen, some product may be lost when separated or collected
Why should chemical manufacturers use reactions with high yields?	To help conserve resources, reduce waste and pollution
What is a reversible reaction?	A reaction that can go both forwards and backwards, or both ways or in both directions
What method can be used to analyse the colours in food?	Paper chromatography
What is the main purpose of the gas chromatography column in GC -MS analysis?	To separate the compounds (in the mixture)
How is the relative molecular mass shown in a mass spectrum?	From the molecular ion peak or the peak with the largest mass (furthest to the right in the spectrum)
There are two main types of chlorine atom, 35/17Cl and 37/17Cl (Mass number + Atomic Number) What name is used for these two types of atom?	Isotopes
There are two main types of chlorine atom, 35/17Cl and 37/17Cl (Mass number + Atomic Number) How is an atom of 35/17Cl different from an atom of 37/17Cl	35/17 Cl has two fewer neutrons than 37/17 Cl (18 neutrons compared with 20 neutrons)
Hydrogen and iodine react to make hydrogen iodine. The equation for the reaction is: H2 + I2 =2Hl What type of reaction is this?	Reversible
What substances in foods can be detected by paper chromatography?	(Artificial) colours
What is the relative formula mass of magnesium fluoride, MgF2?	62
What is the mass of one mole of aluminium oxide, Al2O3?	102g
What is the percentage by mass of copper in copper (II) carbonate, CuCo3?	51.4% (51%)
A student made some magnesium oxide by burning magnesium in air. The student obtained a yield of 55%. Suggest two reasons why the yield was less than 100%	Two from: Magnesium oxide was lost or not collected, the magnesium did not all react, magnesium reacted with other substances in air
What is the empirical formula of vanadium oxide that contains 56% of vanadium?	V2O5
Calculate the mass of zinc chloride that you can make from 6.5g of zinc Zn +2HCl --> ZnCl2 +H2	13.6g
Calculate the percentage yield if 9.0g MgSO4 was made from 4.0g MgO	75%
What information can be obtained from the molecular ion peak in a mass spectrum?	Relative molecular mass (of the compound)

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	Criado por Mel Hughes quase 8 anos atrás