General Chemistry Answers

While work‎ing in a metal proc‎essing facility, Letlen had accide‎ntally mixed two me‎tal vats toge‎ther rea‎ting an alloy. On‎e vat ‎was lab‎eled for cadmium, w‎hile the other was not. It can be ass‎umed that he‎se are of pure metal comp‎osition. To identify this metal, Letlen took 1.000 g of the homogenous alloy ample composed of cadmium and the unknown metal, dissolved, and diluted it to exactly 100.0 mL in a volumetric flask. A 20.00-mL aliquot was taken and titrated this using 22.82 mL of 0.05000 M EDTA

MW: Cd (112.411 g/mol)

a. Calcul‎ate the moles of Cd and the m‎oles of unkno‎wn metal in the 20.00‎-mL aliquot.

b. Calc‎ulate the mo‎les of Cd and the mo‎les of unk‎nown metal in the s‎ample.

c. Calc‎ulate the mass (in g) of Cd and the m‎ass (in g) of unk‎nown metal in the sam‎ple.

d. Wh‎at is the MW (in g/mol) of the unkn‎own met‎al?

e. What is the ide‎ntity of the unkno‎wn met‎al that Letlen accid‎entally mix‎ed?

Two analy‎sts deter‎mined compos‎ition of a 2.500-g s‎oda ash sa‎mple. They divid‎ed s‎ample into two equa‎l 1.250-g par‎ts and analyz‎ed it separa‎tely through do‎uble indi‎cator titrat‎ion.

One of them dissolved sample in water to prepare a 250.0 mL stock solution. A 50.00 mL aliquot was titrated using 0.10 M HCl. A volume of 40.08 mL was measured using phenolphthalein indicator and 13.58 mL with the methyl orange indicator.

Another al‎so also dissolved sample in water to prepare a 250.0 mL stock solution. However, they spilled the primary standard, 100% pure Na2CO3, in the solution. They titrated a 50.00 mL aliquot using 0.10 M HCl same way first one did. For methyl orange indicator, they measured a volume of 30.07 mL

MW: NaOH (40.00 g/mol), Na2CO3 (105.99), NaHCO3 (84.01)

a. What is/are component/s of original soda ash sample?

b. What is/are %composition (in %w/w) of original soda ash sample?

c. How much Na2CO3 (in grams) did second spill in solution?

Hint: You do not need vph to solve this

How many moles are in 987.0 grams of Ra(OH)2

1. Coal gasification converts coal into a combustible mixture of carbon monoxide and hydrogen, called coal gas, in a gasifier: H2Oq) + C(s) –→ CO(g)+ H2(g) AHo = ? Calculate the standard enthalpy change for this reaction from the following chemical equations: 2 C(s) + O2(g)→ 2 CO(g) AHo = -222 kJ 2 H2(g) + O2(g) → H2O1) → 2H2O(g) AHo = -484 kJ H2O(g) AHo = +44 kJ This coal gas can be used a fuel: CO(g) + H2(g) + O2(g) CO2(g) + H2O(g) 2. Predict the change in enthalpy for this combustion reaction from the following equations: 2 C(s) + O2(g) → 2 CO(g) AHo = -222 kJ C(s) + O2(g) 2 Н(9) + Ог(g) → CO2(g) AHo = -394 kJ 2H2O(g) AHo = -484 kJ 3. Use the following calorimetrically determined enthalpy changes to predict the standard enthalpy change for the reaction of ethene with chlorine gas. C2H4(g) + Cl2(g) → C2H3C1(g) + HCl(g) AHo = ? H2(g) + Cl2(g) → 2HCI(g) AHo = -185 kJ C2H4(g) + HCl(g) → C2H5C11) AHo = -65 kJ C2H3C1(g) + H2(g) → C2H5C14) AH. = -140 kJ

Sodium carbonate reacts with Sulphuric Acid. What is the balance chemical equation for the reaction?

Given the following reaction:

N2 (g) + 3H2 (g) → 2NH3 (g)

How would the rate of change for NH3 compare to the rate of change for N2?

1. What are buffers?

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2. Write equations to show the dissociation of the salts (i) ammonium chloride and (ii) sodium acetate.

I. __________________________________________________________________

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II. __________________________________________________________________

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3. Write equations to show the hydrolysis of the two salts named in Exercise 2.

I. __________________________________________________________________

II. ________________________________________________________________

4. Calculate the pH of the ammonium chloride solution of concentration 0.1M if the acid dissociation constant/ hydrolysis constant for the NH₄⁺ ion is 5.8 x 10^-10

1 A substance that when dissolved in water increases the concentration of H ions is a/an ……….

2 What is the solubility product (Ksp ) expression? CaF2 (s) ⇌ Ca 2+(aq) + 2F -(aq)

3 What is the pH of 500 mL of solution containing 0.0124 grams of Ca(OH)2?

4 which reactions would increasing pressure at constant temperature not change the

concentrations of reactants and products, based on Le Chatelier's principle?

5 Fill in Each blank cell with the correct value

pH [H +] / M pOH [OH -] / M

2.3 ------------ --------- -------------

12.2 ----------- ---------- --------------

------- 5.1 × 10 -5 ------------- ---------------

-------- ----------- ------------- 7.9 × 10 -- 10

How many grams of CaSO4 (molar mass= 136.2g/m) can be produced from the reaction if 42.528 grams of CaBr2 is reacted with 42.39 grams of LiSO4?

If 15.0 of phosphoric acid completely neutralizes 38.5mL of 0.150 mol/L sodium hydroxide, what is the concentration of the phosphoric acid