6135035
Description
Flashcards by Mel Hughes, updated more than 1 year ago
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Created by Mel Hughes
over 8 years ago
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| Question | Answer |
| 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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