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andreev551 [17]
3 years ago
7

Calculate the enthalpy for the following reaction. During the reaction, the temperature changes from 42.5 C to 37 C. The specifi

c heat of HCl is 4.04J/g*C. Is the reaction endothermic or exothermic?
Chemistry
1 answer:
Dahasolnce [82]3 years ago
4 0

Answer:

q = 0.810 Kj/mol

Its an endothermic reaction

Explanation:

Enthalpy can be evaluated by using following formula -

q = m * c* \delta T

where

q is the enthalpy or change in internal energy

m is the mass in kg

c is the specific heat

and \delta T is the change in temperature

Mass of HCl is equal to 36.46 g/mol

or

Mass of HCl is equal to 0.03646  Kg/mol

Substituting the given values in above equation, we get-

q = 0.03646 * 4.04 * (42.5 - 37)\\q = 0.03646 * 4.04 * 5.5 \\

q = 0.810 Kj/mol

Enthalpy is positive thus it is an endothermic reaction

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If the conjugate base of a molecule has a pkb of 1.4, what would you expect the molecule to be?
maw [93]

If the conjugate base of a molecule has a pKb of 1.4, the molecule should be a Weak Acid.

Notice this question gives us the pKb of the molecule, not the pKa. Because of this, the pH scale basically gets reversed, so lower numbers in pKb correlate with stronger bases, and higher numbers in pKb correlate with stronger acids - the exact opposite of the pH scale.

It's important to make sure you completely understand the terms of conjugate base, conjugate acid, pKb, pKa, and how they all relate. It's easy to mix up the meanings of these definitions.

Here are the two other pieces of information you need to know to correctly answer this question:

  • Strong acids have a weak conjugate base.
  • Strong bases have a weak conjugate acid.

So if the problem says you have a strong conjugate base, then the molecule must be a weak acid. To illustrate this, think of ammonium, NH4+. Ammonium is a weak acid, but the conjugate base of ammonium is ammonia, NH3, which is a reasonably good base.

Learn more about conjugate base here : brainly.com/question/22514615

#SPJ4

3 0
2 years ago
How many neutrons does the most common isotope of hydrogen have?
Lorico [155]
Protium - the most common isotope of hydrogen - has no neutrons in its nucleus.
3 0
3 years ago
The change of phase from a vapor to a liquid is called _____. evaporation condensation distillation vaporization
anastassius [24]
Its condensation

the vapour has a lot of kinetic energy but if it cools down it loses that energy and condenses into a liquid 

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5 0
2 years ago
Read 2 more answers
4. Ammonia is produced by the chemical reaction of nitrogen and hydrogen. N2 (g) + 3H2(g) →→ 2NH3 (9) (A) Calculate the number o
Makovka662 [10]

Answer:

a) No. of moles of hydrogen needed = 5.4 mol

b) Grams of ammonia produced = 27.2 g

Explanation:

N_2 (g)  +  3H_2(g) \rightarrow 2NH_3 (g)

a)

No. of moles of nitrogen = 1.80 mol

1 mole of nitrogen reacts with 3 moles of hydrogen

1.80 moles of nitrogen will react with

                               = 1.80 × 3 = 5.4 moles of hydrogen

b)

No. of moles of hydrogen = 2.4 mol

It is given that nitrogen is present in sufficient amount.

3 moles of hydrogen produce 2 moles of NH_3

2.4 moles of hydrogen will produce

                              = \frac{2}{3} \times 2.4 = 1.6\ mol\ of\ NH_3

Molar mass of ammonia = 17 g/mol

Mass in gram = No. of moles × Molar mass

Mass of ammonia in g = 1.6 × 17

                                    = 27.2 g

7 0
3 years ago
Polyglutamate also exhibits pH-dependent unfolding. This transition occurs at a pH of about 7; below that pH the polypeptide cha
Novosadov [1.4K]

Answer:

Explanation:

As the pH drops, the NH2groups on the lysine side chains become charged and helices can no longer form because of charge repulsion between these groups. This might occur below the pKa of lysine if more than 50% of the lysine residues is to be charged in order to ‘break’ the helix. Another possibility is that the pKa of lysine residues might be different when in polylysine as compared with the monomer (free amino acid) in solution.

One will expect other residues that are positively charged at neutral pH to have a similar profile; namely, arginine and possibly histidine. Both arginine and histidine are bulkier than lysine. Even if there were some rotation of their side chains, steric interference would probably be so severe as to prohibit the formation of an -helix. The transition is inverted because at a low pH glutamate will be neutral whereas at a high pH it will assume a net negative charge (through dissociation of the carboxyl groups on its side chains). One will easily speculate that a polypeptide chain containing both glutamate and lysine residues will be able to form an helix at relatively neutral pHs. Under these conditions, lysines will be mostly positively charged and glutamates will be mostly negatively charged. This will allow these residues to make ionic bonds and salt bridges to stabilize the helix. At very low pH, however, lysine will be mostly positively charged, but it will be near to neutral glutamate residues. At very high pH, the Glu will be negatively charged, but it will be near neutral.

5 0
2 years ago
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