How much heat in kilojoules is evolved in converting 2.00 mol of
steam at 140 ∘C∘C to ice at -20.0 ∘C∘C? The heat capacity of steam
is 1.84 J/g∘CJ/g∘C and that of ice is 2.09 J/g∘CJ/g∘C.
Remember that if heat is leaving the system, then q is a negative
number and if heat is entering the system, then q is a positive
number.
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b) Calcium hydroxide, Ca(OH)2, is an important component of many mortars, plasters and cements. Calculate the molar solubility of Ca(OH)2 in water if Ksp is 6.5 x 10-6.
c) What is the solubility of Ca(OH)2 in a 0.20 M solution of Ca(NO3)2? Ksp of Ca(OH)2 is 6.5 x 10-6
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1) If the Ka of a monoprotic weak acid is 2.1
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How many grams of NaH2PO4 and how many grams of Na2HPO4 are needed to prepare 2.0 L of 1.50 M “phosphate buffer” with a pH of about 8.00.
You are given:
For salt form of a weak acid NaH2PO4 or weak acid H2PO4-, pKa = 7.21 and Ka = 6.2 x 10-8
1 mol Na2HPO4 = 142 g Na2HPO4
1 mol NaH2PO4 = 120 g NaH2PO4
Select one:
a. Mass of NaH2PO4: 35.5 g and Mass of Na2HPO4: 276.1 g
b. Mass of NaH2PO4: 70.6 g and Mass of Na2HPO4: 392.9 g
c. Mass of NaH2PO4: 50.2 g and Mass of Na2HPO4: 366.5 g
d. Mass of NaH2PO4: 37.9 g and Mass of Na2HPO4: 312.8 g
e. Mass of NaH2PO4: 75.3 g and Mass of Na2HPO4: 408.1 g
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A mixture solution of Co(II) and Ni(II) shows an absorbance of 0.500 at 500 nm. What percentage of incident light is absorbed by the solution?
Under the given conditions if 20% of the absorbance is ascribed to the contribution of Co(II), what will the absorbance of Ni(II) be?
In: Chemistry
In: Chemistry
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An atom of an element weighs 5.88 × 10-23 g. What is the atomic mass of this element in atomic mass units?
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1. When chromium metal is added to nitric acid, the following reaction takes place Cr (s) + 6 HNO₃ (aq) → Cr(NO₃)₃ (aq) + 3 H₂O (l) + 3 NO₂ (g) Calculate the volume of NO₂ gas collected over water at 40.0 °C when 35.1 g of chromium is added to excess nitric acid if the total pressure is 675 torr. The vapor pressure of water at 40.0 °C is 55.3 torr.
and
2. How many grams of Al were reacted with excess HCl if 6.28 L of hydrogen gas were collected at STP in the following reaction? 2 Al (s) + 6 HCl (aq) → 2 AlCl₃ (aq) + 3 H₂ (g)
In: Chemistry
1.
An aqueous solution of calcium hydroxide is
standardized by titration with a 0.171 M solution
of hydroiodic acid.
If 27.0 mL of base are required to neutralize
10.6 mL of the acid, what is the molarity of the
calcium hydroxide solution?
_______M calcium hydroxide
An aqueous solution of hydrobromic acid is
standardized by titration with a 0.162 M solution
of calcium hydroxide.
If 23.9 mL of base are required to neutralize
27.6 mL of the acid, what is the molarity of the
hydrobromic acid solution?
_______M hydrobromic acid
2.
A 12.2 g sample of an aqueous solution of
hydroiodic acid contains an unknown amount of the
acid.
If 24.1 mL of 0.305 M
barium hydroxide are required to neutralize the
hydroiodic acid, what is the percent by mass of
hydroiodic acid in the mixture?
______% by mass
A 11.1 g sample of an aqueous solution of
hydrobromic acid contains an unknown amount of the
acid.
If 22.4 mL of 0.467 M
barium hydroxide are required to neutralize the
hydrobromic acid, what is the percent by mass of
hydrobromic acid in the mixture?
______% by mass
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The human body contains 0.20% natural potassium. K-40 represents 0.0117% of naturally occurring potassium. 1. What is the radioactivity due to K-40 for a person weighing 70 kg? 2. What is the radioactivity due to K-40 for all people on Erath?
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by comparing the instrumental design of a spectrophotometer and the spectrofluorometer, why does the emission spectrum of the blank have well defined peaks while the absorption spectrum is nearly flat?
(hint how do you define absorbance)
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What are some medical or commercial applications of gases, and how are gas laws a part of those applications? Post a thorough initial response to the discussion question (at least 7-10 sentences, or approximately 150-200 words).
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What must be the molarity of an aqueous solution of NH3 if it is 4.3 % ionized? Express your answer using two significant figures.
In: Chemistry