How many gram of Sodium chloride is needed to prepare 47ml of 7% NaCl solution?
Answers
Answer:
5gm
Explanation:
mark me as brainlist
Answer:
There are a few problems here!
Do you mean weight percent or weight/volume %
many times with solids such as this they use weight/volume % (which isn’t a true percentage).
Also 7% NaCl has a density (in grams/cm3) which changes with temperature. Therefore we would need to know the temperature and the density of that concentration, to get a true value.
We could do a calculation using true percent, which would be in grams/100grams. we could then multiply by 10 to give us grams/1000ml. We could then divide by the molar mass (or formula weight of NaCl) to give us moles per 1000cm3, which is molarity. However the answer is basically just an exercise in mathematics.
The next problem is the molarity of the 6M sodium chloride. Once you get above 1 molar; you really should use activity (along with an activity coefficient) and Molality (grams/Kg). The reason being 6M sodium chloride is very concentrated and so the effective molarity would be no where near 6M because of ion and molecular cohesive forces! Although I’m not an expert in this area and I am not quite sure of the effect of this, if any on this calculation.
if we ignore the above it would then just be a simple matter of allowing for the change in volume.
I’m sure all this is more than what you bargained for but I thought you should be aware of it. Always specify the units of your percentage solution!
There are other answers shown where they have started from a 6moles/1000ml solution of NaCl. Then divided by 1000 and multiplied by 250 to give 1.5 moles.
Multiplied by the molar mas of 58.44g/mol .However they have rounded off before the end of the calculation which causes error and gives an incorrect answer. Never round-off till you get to the end of a calculation! Then give your answer to the amount used with the least number of sig figs! The amount they should have used is 87.66 grams!
The next step involves dividing 7% by 100; and then multiplying by 130ml.
to give 9.1g.
I will let you do the last part.
Good luck!