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How should the concentration of a colour sample be determined
Match the enzyme catalysed chemical reaction with the correct class of enzyme for that reaction
1. An 8.00 mg sample of an organic compound was
subjected to quantitative combustion to give 15.33 mg
of carbon dioxide and 9.36 mg of water. The
molecular weight was found to be 46. Calculate the %
composition, empirical and molecular formula of the
organic compound.
aluminum-27 absorbs an electron to form magnesium-27
1. An organic compound is known to be nonvolatile and non-electrolyte. A 0.35- g sample is dissolved in water and diluted to 150mL. The osmotic pressure is measured as 0.04 atm at 25ºC. The approximate mass number for this compound is 1400g/mol. From the data provided in this problem and knowing that the density of the solution is 1.00g/mL
a. Calculate the freezing point of the solutions
b. Determine if the freezing point change would be a good way to determine the molecular mass of the compound
c. Would the boiling point change be a better determining factor than the freezing point change?
Salt is often used to melt ice and snow on roads in the winter and the temperature right now is -4.500ºC. How much NaCl (complete dissociation) would be necessary to melt 1000kg of ice by bringing down the freezing temperature to - 4.500ºC?
A solution was produced by dissolving 3.75 g of a nonvolatile solute in 95g of acetone. The boiling point of pure acetone was observed to be 55.95 ºC, while the boiling point of the solution was 56.50ºC. If the boiling point for acetone is 1.71ºC/m, what is the approximate molar mass of solute?
Step 1: First compute the molality of the boiling point equation.
Step 2. Then, from the definition of molality, compute the number of moles solute, n(solute), in the sample.
Step 3. Solve for the molar mass.
A solution containing 4.50 g of a non-electrolyte (i=1) dissolved in 125 g of water freezes at -0.372ºC. Calculate the molar mass of the solute.
Step 1: First compute the molality of the freezing point equation.
Step 2. Then, from the definition of molality, compute the number of moles solute, n(solute), in the sample.
Step 3. Solve for the molar mass
Write an essay on the topic “When are colligative properties considered beneficial to life?”
a)
An increase in the ionisation of a molecule in a GI environment will usually
increase its solubility. Valproic acid is an oral dosage form used in epilepsy and
has a pKa of 4.8. With the stomach pH at 2.0 and the ileum at pH 6.8, which area
of the GIT will Valproic acid be more soluble.
b)
You are required to manufacture 1L of 50mM pH 7.0 phosphate buffer that could be
used for an injectable formulation of valproic acid. The Ka of dihydrogen phosphate is
6.3x10
-8
and the RMM of potassium dihydrogen phosphate and dipotassium
hydrogen phosphate are 136 and 174 respectively.
I.
Calculate the pKa of dihydrogen phosphate.
II.
What is the ratio between the conjugate base and the acid to be used?
III.
Calculate the mass of anhydrous potassium dihydrogen phosphate and
dipotassium hydrogen phosphate with RMM of 136 and 174, and
concentrations of 30.5 and 19.5 mmol respectively.
