10. A student weight out a 25 g sample of NaCl, SiO2 and NH4Cl. The student determines the sample contains 3.0 g NH4Cl and 7.0 g SiO2. What is the percentage of NaCl by mass (weight) in the sample?
mass NaCl = 25.0g-mass NH4Cl - mass SiO2.
% NaCl = (mass NaCl/mass sample)*100 = ?
To find the percentage of NaCl by mass in the sample, we need to determine how much NaCl is present in the sample.
Given:
Total weight of the sample = 25 g
Weight of NH4Cl = 3.0 g
Weight of SiO2 = 7.0 g
To find the weight of NaCl, we can subtract the weights of NH4Cl and SiO2 from the total weight of the sample:
Weight of NaCl = Total weight of the sample - Weight of NH4Cl - Weight of SiO2
= 25 g - 3.0 g - 7.0 g
= 15 g
Now, to calculate the percentage of NaCl by mass in the sample, we divide the weight of NaCl by the total weight of the sample and multiply by 100:
Percentage of NaCl = (Weight of NaCl / Total weight of the sample) * 100
= (15 g / 25 g) * 100
= 60%
Therefore, the percentage of NaCl by mass in the sample is 60%.