0.12 g of rock salt(NaCl and impurities) was dissolved in water and titrated with 0.1 M silver nitrate. 19.7 mL was required to titrate all the chloride ion. How many moles of sodium chloride were in the original sample and what percent of the sample are impurities?
moles Ag^+ used = M x L = xx.
mols Cl^- in sample = xx.
g Cl^- = mols Cl^- x atomic mass Cl.
0.12 - g Cl = g impurities.
To find the number of moles of sodium chloride (NaCl) in the original sample, we need to use the balanced chemical equation for the reaction between silver nitrate (AgNO3) and sodium chloride (NaCl):
AgNO3 + NaCl -> AgCl + NaNO3
From the balanced equation, we can see that 1 mole of AgNO3 reacts with 1 mole of NaCl to form 1 mole of AgCl.
Given that it took 19.7 mL of 0.1 M silver nitrate (AgNO3) to titrate all the chloride ions, we can calculate the number of moles of Cl- ions present in the original sample.
19.7 mL * 0.1 mol/L = 1.97 mmol (millimoles)
Since NaCl has a 1:1 molar ratio with Cl-, we know that there are also 1.97 mmol of NaCl in the original sample.
To convert millimoles to moles, we divide by 1000:
1.97 mmol / 1000 = 0.00197 moles
Therefore, there are 0.00197 moles of sodium chloride (NaCl) in the original sample.
To determine the percentage of impurities, we need to subtract the moles of NaCl from the moles of the total sample. The molar mass of NaCl is approximately 58.44 g/mol.
0.00197 moles of NaCl * 58.44 g/mol = 0.115 g of NaCl
Since the original sample weighed 0.12 g, the mass of the impurities can be calculated as follows:
Mass of impurities = Total mass - Mass of NaCl
Mass of impurities = 0.12 g - 0.115 g = 0.005 g
To find the percentage of impurities, we divide the mass of impurities by the total mass of the sample and multiply by 100:
Percentage of impurities = (Mass of impurities / Total mass) * 100
Percentage of impurities = (0.005 g / 0.12 g) * 100 = 4.17%
Therefore, approximately 0.00197 moles of sodium chloride (NaCl) were in the original sample, and about 4.17% of the sample consists of impurities.
To find the number of moles of sodium chloride (NaCl) in the original sample and the percent of impurities, we need to follow these steps:
Step 1: Calculate the number of moles of silver nitrate (AgNO3) used in the titration.
Using the formula for molarity (M) and volume (V), we can determine the number of moles (n) of AgNO3 used:
n(AgNO3) = M(AgNO3) * V(AgNO3)
n(AgNO3) = 0.1 mol/L * 19.7 mL * (1 L / 1000 mL) [Converting mL to L]
Step 2: Determine the number of moles of chloride ion (Cl-) in the sample.
Since AgNO3 reacts with Cl- in a 1:1 ratio (as per the balanced equation), the number of moles of AgNO3 used will be equal to the number of moles of Cl- in the sample.
Number of moles of Cl- = n(AgNO3)
Step 3: Calculate the number of moles of NaCl in the sample.
Since NaCl contains one mole of Cl- per mole of NaCl (as per the balanced equation), the number of moles of Cl- is equal to the number of moles of NaCl.
Number of moles of NaCl = n(Cl-)
Step 4: Calculate the mass of NaCl in the original sample.
Using the molar mass of NaCl (58.44 g/mol), we can convert the number of moles of NaCl into grams.
Mass of NaCl = Number of moles of NaCl * Molar mass of NaCl
Step 5: Calculate the mass of impurities.
The mass of impurities can be determined by subtracting the mass of NaCl from the total mass of the original sample.
Mass of impurities = Mass of the sample - Mass of NaCl
Step 6: Calculate the percent of impurities.
The percent of impurities can be calculated by dividing the mass of impurities by the mass of the original sample and multiplying by 100.
Percent of impurities = (Mass of impurities / Mass of the sample) * 100
Now let's plug in the values and calculate the results:
Given: V(AgNO3) = 19.7 mL, M(AgNO3) = 0.1 mol/L, and mass of the original sample = 0.12 g.
Step 1: Calculate the number of moles of silver nitrate (AgNO3) used in the titration.
n(AgNO3) = 0.1 mol/L * 19.7 mL * (1 L / 1000 mL)
n(AgNO3) = 0.00197 mol
Step 2: Determine the number of moles of chloride ion (Cl-) in the sample.
Number of moles of Cl- = n(AgNO3) = 0.00197 mol
Step 3: Calculate the number of moles of NaCl in the sample.
Number of moles of NaCl = n(Cl-) = 0.00197 mol
Step 4: Calculate the mass of NaCl in the original sample.
Mass of NaCl = Number of moles of NaCl * Molar mass of NaCl
Mass of NaCl = 0.00197 mol * 58.44 g/mol
Mass of NaCl = 0.115 g
Step 5: Calculate the mass of impurities.
Mass of impurities = Mass of the sample - Mass of NaCl
Mass of impurities = 0.12 g - 0.115 g
Mass of impurities = 0.005 g
Step 6: Calculate the percent of impurities.
Percent of impurities = (Mass of impurities / Mass of the sample) * 100
Percent of impurities = (0.005 g / 0.12 g) * 100
Percent of impurities = 4.17%
So, there were approximately 0.00197 moles of sodium chloride (NaCl) in the original sample, and the percent of impurities was approximately 4.17%.