The melting point of bulk gold is 1064 C. In a melting experiment, it was found...
The melting point of bulk gold is 1064 C. In a melting experiment,
it was found that a gold nanocrystal of 5.0 nm in diameter has a
melting point of 817 C, and an unknown gold nanocrystal has a
melting point of 500 C. Estimate the particle size of this unknown
gold sample.
Homework Answers
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The melting point of bulk gold is 1064 C. In a melting
experiment,
it was found...
(a) For the solidification of pure gold compute the critical radius r and the activation energy...
(a) For the solidification of pure gold compute the critical radius r and the activation energy AG* if nucleation is homogeneous. Values for the latent heat of fusion and surface energy are -1.16x109 J/m3 and 0.132 J/m2 respectively. AT for gold is 230°c from Table 11.1, Tm for gold is 1064°C (b) Calculate the number of atoms found in a nucleus of critical size. Assume a lattice parameter of 0.413 nm for solid gold at its melting temperature.
(a) For...
A unknow compound was found to have an experiment melting point , MPexp, of 126.0-130.2 degree...
A unknow compound was found to have an experiment melting point , MPexp, of 126.0-130.2 degree Celsius.Assume the thermometer in the experiment was pre -calibrated to read accurate temperature.(a) .Comment on the purity of the unknow. Briefly explain. (b) . Achemist is given a list of possible identities for the solid unknown. which is the likely identity? Explain your decision. Compound melting point. A 87.5-88.5 degree Celsius B 125.5-127.0 degree Celsius C 132.5-134.5 degree celsius
Cinnamic acid and urea melt at 133°C. The melting point of an unknown is found to...
Cinnamic acid and urea melt at 133°C. The melting point of an unknown is found to be 133°C. What experiments using melting range determinations could be done to determine if the unknown is cinnamic acid or urea?
8. Metals can exist as liquids at hundreds of degrees below their melting point. The normal...
8. Metals can exist as liquids at hundreds of degrees below their melting point. The normal melting point of gold is 1064°C where AH fus = 12.55 kJ mol-. Deeply supercooled gold has been observed at 834°C. Given that Cp.m(s) = 25.418, and Cpm(l) = 29. 29 J mol-? K-, consider the change in entropy when one mole of supercooled gold at 834°C freezes isothermally. Determine AS for a) the system (the gold) and [-20 < AS <OJ K-] b)...
3. A sample taken on a melting point apparatus was found to melt at 134.2-135.0°C. The...
3. A sample taken on a melting point apparatus was found to melt at 134.2-135.0°C. The compound is either malonic acid, or acetylsalicylic acid. Assuming availability of malonic acid and acetylsalicylic acid, as well as the sample, how would you determine if the sample was malonic acid or acetylsalicylic acid? (Use only the concepts introduced in this experiment, and describe all expected observations!)
In a differential scanning calorimetry experiment, the melting temperature, Tm, of a certain protein is found...
In a differential scanning calorimetry experiment, the melting temperature, Tm, of a certain protein is found to be 46 C and the enthalpy of denaturation is 382 kJ/mol. a. Estimate the entropy of denaturation assuming that the denaturation is a two-state process; that is: native protein<=>denatured protein. b. The single polypeptide protein chain has 122 amino acids. Calculate the entropy of denaturation per amino acid. Comment on your results.
An unknown compound gave a melting point of 230 °C. When the melted liquid solidified, it...
An unknown compound gave a melting point of 230 °C. When the melted liquid solidified, it was melted again and found to have a melting point of 150 °C. Give a possible explanation.
Two metals A (melting point 800°C) and B (melting point 650°C) form a binary isomorphous system....
Two metals A (melting point 800°C) and B (melting point 650°C) form a binary isomorphous system. An alloy containing 45 wt% metal B is found to consist of 75 wt% solid and the remainder liquid whereas an alloy containing 55 wt% metal B is found to consist of 35 wt% solid at 700°C. Draw the phase diagram that you would expect for this alloy system and estimate the composition of the solidus and the liquidus at 700 °C
- A student is trying to identify an unknown solid based on its melting point. She...
- A student is trying to identify an unknown solid based on its melting point. She noted that the compound began to melt at 182°C and finished melting at 187°C. Knowing it is possible for there to be impurities in the sample, is this compound more likely to be camphor or hydroquinone. Explain your reasoning. A young chemist has synthesized what he believed to be acetaminophen. He measured the melting point of this newly formed compound to be 163-178°C. If...
A solid unknown has a melting point range of around 115-117 deg C and has a...
A solid unknown has a melting point range of around 115-117 deg
C and has a IR spectrum shown below. What is the likely
structure/name of the compound?
(a) For the solidification of pure gold compute the critical radius r and the activation energy AG* if nucleation is homogeneous. Values for the latent heat of fusion and surface energy are -1.16x109 J/m3 and 0.132 J/m2 respectively. AT for gold is 230°c from Table 11.1, Tm for gold is 1064°C (b) Calculate the number of atoms found in a nucleus of critical size. Assume a lattice parameter of 0.413 nm for solid gold at its melting temperature.
(a) For...
Cinnamic acid and urea melt at 133°C. The melting point of an unknown is found to be 133°C. What experiments using melting range determinations could be done to determine if the unknown is cinnamic acid or urea?
8. Metals can exist as liquids at hundreds of degrees below their melting point. The normal melting point of gold is 1064°C where AH fus = 12.55 kJ mol-. Deeply supercooled gold has been observed at 834°C. Given that Cp.m(s) = 25.418, and Cpm(l) = 29. 29 J mol-? K-, consider the change in entropy when one mole of supercooled gold at 834°C freezes isothermally. Determine AS for a) the system (the gold) and [-20 < AS <OJ K-] b)...
3. A sample taken on a melting point apparatus was found to melt at 134.2-135.0°C. The compound is either malonic acid, or acetylsalicylic acid. Assuming availability of malonic acid and acetylsalicylic acid, as well as the sample, how would you determine if the sample was malonic acid or acetylsalicylic acid? (Use only the concepts introduced in this experiment, and describe all expected observations!)
- A student is trying to identify an unknown solid based on its melting point. She noted that the compound began to melt at 182°C and finished melting at 187°C. Knowing it is possible for there to be impurities in the sample, is this compound more likely to be camphor or hydroquinone. Explain your reasoning. A young chemist has synthesized what he believed to be acetaminophen. He measured the melting point of this newly formed compound to be 163-178°C. If...
A solid unknown has a melting point range of around 115-117 deg
C and has a IR spectrum shown below. What is the likely
structure/name of the compound?
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