Review your understanding /33 |
1) Non metal X can be identified from its relative isotopic masses. The table below shows the abundances of the isotopes:
Isotope | Isotope 1 | Isotope 2 |
Relative isotopic mass | 37 | 35 |
% abundance | 25.0 | 75.0 |
a) Define relative atomic mass [2]
b) Calculate the relative atomic mass of a sample of X. Give your answer to 3 significant figures. [2]
c) Use your answer to (b) and the data sheet to identify element X [1]
2) A sample of gas was found to contain 1.630g of carbon and 0.272g of hydrogen by mass and an Mr of 28.
Calculate the molecular formula of this compound. [4]
3) A student added 2.74g of Barium to water according to the following reaction:
Ba(s) + 2H2O(l) à Ba(OH)2(aq) + H2(g)
The resulting solution was then made up to 250cm3 with distilled water.
a) Calculate how many moles of Ba reacted [2]
b) Calculate the volume of hydrogen that would be produced assuming 1 mole of gas occupies 24dm3 [2]
c) Calculate the concentration of the Ba(OH)2 [2]
d) Using oxidation numbers identify which element has been oxidised. [3]
4) A student added magnesium oxide to 25cm3 of 2.00 mol dm-3 nitric acid until all the nitric acid reacted.
a) Write a balanced chemical equation for the above reaction, include state symbols [3]
b) How would the student know when the reaction was complete? [1]
c) Calculate how many mole of nitric acid was used in the reaction [2]
d) Deduce the number of moles of magnesium oxide that reacted with this amount of nitric acid [1]
e) Calculate the mass of magnesium oxide reacted with the nitric acid [3]
5) A 2.95g sample of the hydrated crystal CoI2.nH2O was heated until there was no further change in mass.
The final mass of the anhydrous crystals was 2.19g.
a) Calculate n and give the formula of the salt [3]
b) Write an equation for the change that took place. Include state symbols in your answer [2]