Exercises calculating concentrations

EXAMPLE 10.4 Sample exercise Calculating the hydronium ion concentration from the pH... 

EXAMPLE 10.13 Sample exercise Calculating the concentrations of all solute species in a polyprotic acid solution... 

Prelab Exercise Calculate the volume of hydrogen gas generated when 3 mL of 1 M sodium borohydride reacts with concentrated hydrochloric acid. Write a balanced equation for the reaction of sodium borohydride with platinum chloride. Calculate the volume of hydrogen that can be liberated by reacting 1 g of zinc with acid. 

EXERCISE 18.1 Calculating Concentration from Partial Pressure... 

Practice Exercise Calculate the concentration of OH ions in a HCl solution whose hydrogen ion concentration is 1.3 M. 

Practice Exercise Calculate the concentrations of H2C2O4, HC2O4, C2OI, and ions in a 0.20 AT oxalic acid solution. 

Practice Exercise The concentration of Rn-222 in the basement of a house is 1.8 X 10 mol/L. Assume the air remains static and calculate the concentration of the radon after 2.4 days. 

Problem 2.9. In Section 2.10.2, we calculated the molar concentration of As in an 100-ppm As-doped Si solid solution. Building on that exercise, calculate the mass density (g/cm ) of As in this 100-ppm As-doped Si solid solution. 

Practice Exercise Calculate the molar concentration of oxygen in water at 25°C for a partial pressure of 0.22 bar. 

Cell geometry, such as tab/terminal positioning and battery configuration, strongly influence primary current distribution. The monopolar constmction is most common. Several electrodes of the same polarity may be connected in parallel to increase capacity. The current production concentrates near the tab connections unless special care is exercised in designing the current collector. Bipolar constmction, wherein the terminal or collector of one cell serves as the anode and cathode of the next cell in pile formation, leads to gready improved uniformity of current distribution. Several representations are available to calculate the current distribution across the geometric electrode surface (46—50). 

X 10 14Af (by a factor of 107), reaction (55) must consume about 10-7 mole of hydroxide ion for every liter of solution. Since one mole of OH-(ag) reacts with one mole of H+(aq), the amount of H+(aq) required is also 10-7 mole for every liter of solution. Subtracting 10-7 mole/liter from a concentration near 1 mole/liter causes such a small change in [H+] that it need not be considered in calculations (such as in Exercises 11-1 and 11-2). 

The first strategy is to rmdertake a superficial scan of mainstream textbooks that everyday situations have been connected to cormnon school chemistry textbooks. For example, student-exercises may contain informatiorr, about contaminants in a river such as lead salts, about acid-base indicators in plants or about food additives for the preservation of wine. However, implicit confusion may (and frequently will) occur when the textbook and the teacher aim at reaching the right answer, for example the correct calculation of the concentration of an additive in gram per litre or parts per million (ppm). Students may still pose questions such as How many glasses of wine can I drink before 1 will get sick What is the effect of alcohol on my body Why is the addition of sulphite to wine important Is the same fact tme for red wine Or even further Shouldn t the government prohibit the addition of sulphite In this way students can become personally involved in subjects that can be related to their learning of chemical substances, and even to atoms and molecules. But, the student-activities in mainstream school chemistry textbooks often are not focused on this type of involvement they do not put emphasis in the curriculum on personal, socio-scientific and ethical questions that are relevant to students lives and society. 

C16-0024. Calculate the concentrations of the species present in an aqueous solution of ammonia (see Extra Practice Exercise 16-10) that is 0.0125 M NH3. ... 

Repeat the calculation in Exercise 8 for equilibrium conversion and equilibrium concentration, but taking into account variation of AH° with temperature. Again assume ideal gas behavior. Heat capacity coefficients for Equation 6.42 are given in Table 6.196. 

For the rest of the exercise, the plan is straightforward for the neutralization reaction between HN03 and NaOH, perform the limiting reactant problem. The pH is determined from the concentration of excess HN03 or NaOH. Each calculation is totally independent of the other calculations. 

The absorption of inhaled -hexane has been investigated in six healthy male volunteers (Veulemans et al. 1982). Three different trials were performed on each volunteer 4-hour exposure at 102 ppm -hexane 4-hour exposure at 204 ppm, and exposure during exercise on a stationary bicycle ergometer at 102 ppm. Each trial was done at least two weeks apart. Lung clearance (from alveolar air to blood) and retention were calculated from -hexane concentrations in inhaled and expired air. After exposure, /7-hcxane in exhaled air was measured for up to 4 hours to determine respiratory elimination. Retention of -hexane (calculated from lung clearance and respiratory minute volume) was approximately 20-25%... 

The results of interlaboratory study II are presented in Fig. 4.5.1. Five sets of results were obtained for the LAS exercise, and four sets for the NPEO exercise. For LAS, the within-laboratory variability ranged between 2 and 8% (RSD) for sample III (distilled water spiked with lmgL-1 LAS), 1 and 13% for sample 112 (wastewater influent), and 3 and 8% for sample 113 (sample 112 spiked with lmgL-1 LAS). Between-laboratory variations (calculated from the mean of laboratory means, MOLM) amounted to RSDs of 15, 30 and 30% for samples III, 112 and 113, respectively. The LAS values reported were in the range of 700—1100 p,g L-1 in sample III, 1100-1800 p,g L-1 in sample 112 and 1900-3000 p,g L-1 in sample 113, indicating that even in the matrix wastewater influent, the spiked concentration of lmgL-1 LAS could be almost quantitatively determined by all laboratories. 

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