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PS_11_Group_03

Page history last edited by Elina Rimpivaara 10 years, 6 months ago

EXPERIMENTAL PROBLEM n. 11 GROUP 3

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. Useful knowledge (reference data, concepts and principles)

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:

 

2. Main idea

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.

 

3. Planning

 

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

 

4.  Report

 

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

 

 

 

 

Mass of the empty box 13,5 g

Mass of the box with sample

15,0 g

 

The flame colour is red.

 

 

 

 

 

5. Elaboration and Interpretation

 

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)   

 

 

Salt mass 1,5 g

Metal ion is strontium.

0,0171:2*87,62=0,74477

1,5 - 0,75477 = 0,74523

Common conclusions

 

 

 

Questions & Answers

 

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.

 



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