Chem 321 Exam 1 – Flashcards

A solution of H2SO4(aq) with a molal concentration of 8.01 m has a density of 1.354 g/mL. What is the molar concentration of this solution?

A 18.0 wt% solution of CaCl2 (110.98 g/mol) has a density of 1.165 g/mL. What is the mass (in milligrams) of a 17.6-mL solution of 18.0 wt% CaCl2?

A 18.0 wt% solution of CaCl2 (110.98 g/mol) has a density of 1.165 g/mL. What is the mass (in grams) of CaCl2 in 483.6 mL of a 18.0 wt% solution of CaCl2?

A 18.0 wt% solution of CaCl2 (110.98 g/mol) has a density of 1.165 g/mL. What is the formal concentration of CaCl2 (in molarity) of the 483.6-mL CaCl2 solution described in Part B?

A 5.77 g sample of a solid containing Ni is dissolved in 20.0 mL water. A 5.00 mL aliquot of this solution is diluted to 100.0 mL and analyzed in the lab. The solution was determined to contain 6.81 ppm Ni. Determine the molarity of Ni in the 20.0 mL solution. Determine the mass in grams of Ni in the original sample. Determine the weight percent of Ni in the sample.

77.0 mL of a 1.40 M solution is diluted to a total volume of 278 mL. A 139-mL portion of that solution is diluted by adding 125 mL of water. What is the final concentration? Assume the volumes are additive.

The presence of Pb2 can cause interference in a certain method for the determination of As3 in groundwater. A researcher would like to use this method to determine the amount of As3 in a groundwater sample, but she wants to make sure that the method is sufficiently selective for As3 over Pb2 before she uses the method to test the groundwater sample. The researcher knows that if the concentration of As3 is 200.00 times the concentration of Pb2 , then the relative error is 0.25%. Determine the selectivity coefficient, KAs,Pb, for this method.

Some pain relief creams contain capsaicin as an active ingredient. A researcher is developing a new method to determine the capsaicin content of such pain relief creams. The presence of a similar compound, homodihydrocapsaicin, can interfere with the researcher's method. The researcher knows that the method gives a signal for homodihydrocapsaicin of 6.70 (arbitrary units) when an equimolar solution of capsaicin gives a signal of 49.10. What is the value of the selectivity coefficient of capsaicin with respect to homodihydrocapsaicin, KA,I? If the researcher wants to know the concentration of capsaicin to within ±0.70%, what is the maximum relative concentration of homodihydrocapsaicin (CI/CA) that can be present in the sample?

coefficient of variation

Five mineral samples of equal mass of calcite, CaCO3 (MM 100.085) , had a total mass of 10.1 ± 0.1 g. What is the average mass of calcium in each sample? (Assume that the relative uncertainties in atomic mass are small compared the uncertainty of the total mass.)

A solution of hno3 is standardized by reaction with pure sodium carbonate. A volume of 28.45 ± 0.05 mL of HNO3 solution was required for complete reaction with 0.8952 ± 0.0009 g of Na2CO3, (FM 105.988 ± 0.001). Find the molarity of the HNO3 and its absolute uncertainty. ??????????

A clinic took temperature readings of 250 flu patients over a weekend and discovered the temperature distribution to be Gaussian, with a mean of 101.80°F and a standard deviation of 0.9120. Use this normal error curve area table to find the following values. What is the fraction of patients expected to have a fever greater than 103.81°F? What is the fraction of patients expected to have a temperature between 101.25°F and 102.80°F?

Using graphite furnace atomic absorption spectrometry, the mean cadmium (Cd2 ) content value in a homogenized sample of 40 zebra mussles was found to be 5.30 ppb Cd2 with a standard deviation (s) of 0.29 ppb Cd2 (assume that s is a good approximation of ?). Calculate the 90% and 95% confidence intervals (CI) for: (A) two analyses

formula for confidence interval with z-test

z-test versus t-test

when to use f test

how to known if two standard deviations are different

how to know if two means are significantly different at the 95% confidence level

when would you need to calculate degrees of freedom

equation for calculating t value to compare two means

when to use q test

how to perform q test

how to calculate signal detection limit

how to calculate concentration detection limit

how to calculate lower limit of quantitation

how to calculate slope of calibration curve

primary standard

which make good standard solutions for acid-base neutralization titrations

The concentration of HCl can be determined by titration with a primary standard such as Na2CO3 (sodium carbonate). The titration reaction is CO3 (2-) + 2H+ --> H2O + CO2 What is the concentration of HCl if 35.9 mL of HCl was needed to to react with 0.201 g of Na2CO3 to reach the end point?

how to calculate response factor

Determine the quantity of unknown protein that has an absorbance of 0.225 when a blank has an absorbance of 0.094. The previously determined calibration curve has the form of a straight line with the equation A = 0.0182 × x 0.007, where A is the corrected absorbance and x is quantity of protein in units of ?g.