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Rajul N

Numerade Educator

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Numerade tutor for 4 years
109 Students Helped

Rajul's Quick Ask Videos

05:01
Biology

. (a) At what pH are the concentrations of histidine (+) and
histidine (zwitterion) equal? Explain.
(b) What will the ratio of histidine (zwitterion) /
histidine (+) be at pH 5?
(c) At pH 7?
(d) Why is histidine considered both an acid and a base?
07:59
Chemistry 101

1. The following equation is used to calculate specific heat:
Q = CmΔT
where ΔT represents the change in temperature (final temperature - initial temperature).

2. A 25 g piece of metal is sitting in a beaker of boiling water. The metal is taken out of the beaker and quickly placed in the calorimeter that contains 85 g of water at 25°C. After the metal has released all of its heat, the temperature of the water is 27.5 °C. What is the specific heat of the metal?
mmcmΔTm = mwcwΔTw
2130 J/g°C
0.491 J/g°C
2.30 J/g°C
4135 J/g°C

3. The reaction of a strong acid with a strong base is an exothermic reaction that produces water and heat as products.
exothermic reaction
endothermic reaction
both of them
none of them

4. In this table, the elements are arranged in order of increasing atomic number, certain chemical and physical properties repeat periodically.
decreasing atomic number
increasing atomic number
increasing molecular weight
decreasing molecular weight

5. In the periodic table, each horizontal row of elements is a period.

6. In the periodic table, each column is a group (or family).
07:37
Chemistry 101

Let's summarize what we have discovered so far.
In Step 1, we discovered that the more concentrated the bleach, the faster the color of dye disappeared.
In Step 2, we established that:
Rate = k' [dye] and
k' = k [bleach]^n
Since the bleach is colorless, you will not be able to determine directly what happens to it in the reaction. However, you will be able to deduce the effect of bleach by analyzing the equation k' = k [bleach]^n, which shows how the concentration of excess bleach influences the rate of reaction.
The rate of the reaction can be determined from a kinetic trace of the absorbance of the solution, as it tells us how rapidly the dye disappears. From your first experiment, you know the order of the reaction in dye and the pseudo-rate constant, k'.
The term "pseudo" indicates that k' is a product of the actual rate constant, k, and the concentration of bleach, k' = k [bleach]^n.
Think about what happens to the pseudo-constant, k', when you change the concentration of bleach.
Consider the hypotheses corresponding to the reaction being zeroth, first, or second order in bleach. For each of these three hypotheses, what would be the effect on the kinetic trace of changing the concentration of bleach? Design an experiment that you can use to decide which hypothesis is supported.
06:43
Chemistry 101


1. For n-pentane, C5H12,
the heat of vaporization at its normal boiling point
of 36 °C
is 25.8 kJ/mol.
The entropy change when 1.86 moles of
liquid C5H12 vaporizes
at 36 °C, 1 atm is ?
J/K.
2. For cobalt, Co,
the heat of fusion at its normal melting point
of 1495 °C
is 15.5 kJ/mol.
The entropy change when 2.17 moles of
solid Co melts
at 1495 °C, 1 atm is
? J/K.
02:46
Biology

Biological systems sometimes appear on the surface to break the Second Law of Thermodynamics – by seemingly increasing the order in the overall system. They don't. Why?
08:51
Chemistry 101

TOPIC IS... Simple ionic compounds in healthcare and their uses
(CO 3)
1. Apply the scientific method to propose a hypothesis and set
up an experiment
including positive and negative controls and appropriate units of
measurement.
2. Predict the numbers of protons, neutrons, and electrons given
the atomic symbol or limited information for a specific isotope of
an element and relate them to atomic mass and charge.
3. Determine chemical names and/or chemical formula for diatomic
or simple polyatomic compounds and draw a Lewis structure,
construct a molecular geometry and determine the polarity for a
covalent compound.
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