By: Alex Å., Axeli, alex c. , anis s. , massimiliano s.
You receive a sample of a salt formed by an "s-block" metal and an halogen. The amount of this sample contains as many halogen ions as there are in 1,00 grams of sodium chloride. You have to recognize the metal and the halogen in that salt.
Vi viene assegnato un campione di sale formato da un metallo del "blocco s" e da un alogeno. La quantità di questo campione contene tanti ioni alogenuro quanti ve ne sono in 1,00 g di cloruro di sodio. Dovete riconoscere il metallo e l'alogeno nel sale.
Saat suolanäytteen, joka koostuu alkali- tai maa-alkaliryhmän metallista (=s-ryhmä) ja halogeenista. Näyte sisältää yhtä monta halogeeni-ionia kuin 1,00 grammassa natriumkloridia (NaCl) on kloridi-ioneita. Tehtävänä on tunnistaa, mistä metalli- ja halogeeni-ioneista suola koostuu.
1.1 Colours of alkali metals to the bunsen flame:
Lithium | Sodium | Potassium | Calcium | Strontium | Barium |
deep purple | yellow-orange | lilac | orange+red sparkle | red | green-yellow |
1.2 Atomic relative mass of sodium and chlorine: Na=22.99, Cl=35.45
1.3 Formula Weight of NaCl:
1.4 Formula of a salt formed by Me+ and X- ions:
1.5 Formula of a salt formed by Me2+ and X- ions:
Deduce first the "s" block metal by the flame test. Knowing the weight of the salt we deduce then the halogen atom by a calculation.
1. Weigh the bowl with the salt assigned
2. pouring the metal into another container
3. Weigh conteiner empty
4. take the nickel chromium wire
5. clean in the flame
6. soak the wire in the acid and take a small amount of salt on the wire tip
7. Put on the flame and observe the color of the metal
Italian (29th March and 19th April) We: Alex, Massimiliano, Anis |
Finnish (31.3.2010) |
we took the salt assigned to us, in a tub and we weighed it tube with salt; mass = 3,38g empty tub; mass =1,88g We did the test flame and the result was that the color is scarlet red
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Mass of the empty box 13,5 g Mass of the box with sample 15,0 g The flame colour is red.
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Italian | Finnish |
the cation is strontium salt mass is 3,38-1,88= 1,50g Being strontium ions Sr2+, the formula of our salt is SrX2 Strontium atomic mass is 87,62 amu Proportional number of sodium and chlorine in one gram of NaCl = 1.00 : 58.44 = 0.0171 This amount is equal to the number of halogen atoms in SrX2, while Sr atoms are one half of those: Sr atoms = 0.0171 : 2 = 0,00855 their weight amounts to 0,00855·87.62 = 0,7492 g These can be subtracted from the mass of salt to find the mass halogen= 1,50 - 0,75 g = 0,75 g mass of an X atom = 0,75 g : 0,0171 = 43,9 This is closest to the atomic mass of Chlorine (35,5amu). our salt is strontium chloride (SrCl2)
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Salt mass 1,5 g Metal ion is strontium. 0,0171:2*87,62=0,74477 1,5 - 0,75477 = 0,74523 |
Common conclusions
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Please review these answers one each other
1. Why are atoms emitting light at the flame?
Answer 1
because the atoms are excited by the heat
2. How did you recognize the metal element in the salt?
Answer 2
using flame tests.
3. What measure permitted you to deduce which halogen was in the salt?
Answer 3
the weight of the salt from wich i got the halogen.
4. Does your salt contain more cations or anions?
Answer 4.
our salt contain more anions.
5. Does your salt contain more mass as halide ions or as metal ions or the same?
Answer 5
our salt contain more mass of halide ions.