12 SCH0801NN The Chemistry Of Latent Fi
The Chemistry of Latent Fingerprints KEY
Chemical Reaction
Silver nitrate (AgNO3) can react with the salt (NaCl) left from the perspiration on the friction ridge skin to form solid silver chloride (AgCl) and sodium nitrate. The silver chloride can then be converted to silver oxide (Ag2O), which is dark in color and can be more easily seen.
Challenge
Suppose the fingerprint processing technique that uses silver nitrate to react with the salt from perspiration produced 5.8 x 10-2 grams of silver chloride. How many grams of salt was left by the initial latent fingerprint?
Brainstorm the steps to solve this problem as you recall the steps to solving stoichiometry calculations. Be prepared to explain your solution including your decisions with significant figures and scientific notation to increase accuracy.
Be sure you complete each step of the process:
1. Write the chemical equation.
AgNO3 + NaCl AgCl + NaNO3
2. Balance the chemical equation.
AgNO3 + NaCl AgCl + NaNO3
3. Follow steps to dimensional analysis:
Start with what is given.
5.8 x 10-2 g of AgCl
Set up a series of equivalent measures.
End with your goal.
Solve the problem by cancelling units.
5.8 x 10-2 g AgCl X 1 mol AgCl X 1 mol NaCl X 58.44 g NaCl = 2.365 x 10-2 g NaCl 143.32 g AgCl 1 mol AgCl 1 mol NaCl
Record the appropriate answer with units.
2.4 x 10-2 g NaCl
Chemical Reaction
Silver nitrate (AgNO3) can react with the salt (NaCl) left from the perspiration on the friction ridge skin to form solid silver chloride (AgCl) and sodium nitrate. The silver chloride can then be converted to silver oxide (Ag2O), which is dark in color and can be more easily seen.
Challenge
Suppose the fingerprint processing technique that uses silver nitrate to react with the salt from perspiration produced 5.8 x 10-2 grams of silver chloride. How many grams of salt was left by the initial latent fingerprint?
Brainstorm the steps to solve this problem as you recall the steps to solving stoichiometry calculations. Be prepared to explain your solution including your decisions with significant figures and scientific notation to increase accuracy.
Be sure you complete each step of the process:
1. Write the chemical equation.
AgNO3 + NaCl AgCl + NaNO3
2. Balance the chemical equation.
AgNO3 + NaCl AgCl + NaNO3
3. Follow steps to dimensional analysis:
Start with what is given.
5.8 x 10-2 g of AgCl
Set up a series of equivalent measures.
End with your goal.
Solve the problem by cancelling units.
5.8 x 10-2 g AgCl X 1 mol AgCl X 1 mol NaCl X 58.44 g NaCl = 2.365 x 10-2 g NaCl 143.32 g AgCl 1 mol AgCl 1 mol NaCl
Record the appropriate answer with units.
2.4 x 10-2 g NaCl