12. A student working with RNA used DEPC to inactivate ribonucleases in solution. She performed the

A 3.82-g sample of magnesium nitride is reacted with 7.73 g of water. \mathrm{Mg}_{3} \mathrm{~N}_{2}+3 \mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{NH}_{3}+3 \mathrm{MgO} The yield of MgO is 3.60 g. What is the percent yield in the reaction? А. 99.9 В. 46.6 С. 49.4 D. 78.7 Е. 94.5

For the system methane(1)/ethane(2)/propane(3) as a gas, estimate f, f» fx ¢1. Þ2.and 43 at t = 100°C. P 35 bar, y1 =0.21, and y2 = 0.43: (a) Through application of Eq. (10.64). (b) Assuming that the mixture is an ideal solution.

At 25°C, an aqueous solution containing 35.0 wt% H,SO, has a specific gravity of 1.2563. A quantity of the 35% solution is needed that contains 195.5 kg of H2SO4 a. Calculate the required volume (L) of the solution using the given specific gravity. b. Estimate the percentage error that would have resulted if pure-component specific gravities of H SO4(SG = 1.8255) and water had been used for the calculation instead of the given specific gravity of the mixture.

2.51 A tank contains 20 L of compressed nitrogen at 10 bar and 25 °C. Calculate the maximum work that can be obtained when the gas is allowed to expand reversibly to 1 bar pressure(a) isothermally and (b) adiabatically. The heat capacity of nitrogen at constant volume can be taken to be 20.8 J K mol^-1 independent of temperature.

Three different liquidsare used in the manometer shown here. \text { a. Derive an expression for } P_{1}-P_{2} \text { in terms of } \rho_{\mathrm{A}}, \rho_{\mathrm{B}}, \rho_{\mathrm{C}}, h_{1}, \text { and } h_{2} . D. Suppose fluid A is methanol, B is water, and C is a manometer fluid with a specific gravity of 1.37; pressureP = 121.0 kPa; h= 30.0 cm ; and h2 = 24.0 cm. Calculate P (kPa).

Convert the following from mg/L as CaCO3 to mg/L as the ion or compound: (a) 125.00 mg/L as CaCO3 of CO2 For CO2, assume Z = 2 since dissolved CO2 is indistinguishable from H2CO3 (b) 125.0 mg/L as CaCO3 of Ca(OH)2 (c) 125.00 mg/L as CaCO3 of H3PO4 (d) 125 mg/L as CaCO3 of H2PO4 (e) 125 mg/Las CaCO3 of CI

3.25. WP A mixture is 10.0 mole% methyl alcohol, 75-0 mole% methyl acetate (C,H60,), and 15.0 mole%acetic acid. Calculate the mass fractions of each compound. What is the average molecular weight of the mixture? What would be the mass (kg) of a sample containing 25.0 kmol of methyl acetate?

Problem 3.33 Within a cubic unit cell, sketch the following directions: Required problems are a, d, and g. The remaining problems are optional but are provided for addedpractice. Solutions will be provided for all of these problems.

An experiment is planned to record the change in pH as a powdered base is added to 50 cm3 dilute hydrochloric acid. The method suggested is step 1add dilute hydrochloric acid up to the 50 cm³ mark on a beaker; step 2 add one spatula of the base and stir; step 3measure the pH of the mixture; step 4 repeat steps 2 and 3 until the pH stops changing. (i) State how you could change the method so that the amounts of dilute hydrochloric acid and of the base can be measured more accurately. dilute hydrochloric acid base (ii) During the experiment the pH changes from 2 to 10. If phenolphthalein indicator is added at the beginning of the experiment, a colour change occurs as the base is added. State the colour change that occurs. colour at start ... colour at end .. (iii) Explain, in terms of the particles present, why the pH increases during the experiment.

. Suppose a similar experiment had been done using 1.0 M H;PO4solution as the acid. What would be the stoichiometric ratio of moles of NaOH: moles of H;PO4 at the intersection of the ascending and descending portions of the graph of such an experiment?