How are fossils formed

Electronegativity values increase from left to right across a period in the periodic table because there is an increase in the c

Mademuasel [1]

First, let us define Electronegativity. Electronegativity is "the ability of an atom to attract electrons." In addition, electronegativity increases in elements from left to right, while on the other hand, electronegativity decreases from top to bottom in an element group. It decreases because the atomic radius increases as we go downward an element in the group.

5 0

4 years ago

An aqueous solution of ammonia is found to be basic. This observation can be explained by the net ionic equationHNO3(aq) + H2O(l

jeka57 [31]

Answer:

$NH_3_{(aq)}+H_2O_{(l)}\rightarrow NH_4^+_{(aq)}+OH^-_{(aq)}$

Explanation:

Bases are the species which furnish hydroxide ions in the solution or is capable of forming bonds with electron deficient species as they are electron rich species. When a base accepts a proton, it changes into a acid which is known as its conjugate acid.

Net ionic equation : In the net ionic equations, we are not include the spectator ions in the equations. Only the species which are present in aqueous state dissociate. So, the net ionic equation of aqueous solution of ammonia is shown below as:-

$NH_3_{(aq)}+H_2O_{(l)}\rightarrow NH_4^+_{(aq)}+OH^-_{(aq)}$

6 0

3 years ago

Calculate the weight percent of ascorbic acid in a tablet of Vitamin C from the following data:A 80 mg sample of a crushed Vitam

Lina20 [59]

Answer:

The Answer is 88%

Explanation:

The balanced ionic equation of the reaction

$IO^{3- }+ 8 I^- + 6 H^+ => 3 I^{3- }+ 3 H_2O$

$I^{3-} + 2 S_2O_3^{2-} => 3 I^- + S_4O_6^{2-}$

$C_6H_8O_6 + I^{3- }+ H_2O => C_6H_6O_6 + 3 I^- + 2 H^+$

Looking at the above reactions

The original number of moles of $I^{3-}$ = 3 × number of moles of $IO^{3-}$

= 3 × volume × concentration of $KIO_3$

Note: The formula for number of moles is volume × concentration

$=3 * \frac{40}{1000} * 0.00653 =0.000784$ mol

The number of moles of $I^{3-}$ left after its reaction with ascorbic acid

= $\frac{1}{2}$ x moles of $S_2O_3^{2-}$

= $\frac{1}{2}$ x volume x concentration of $S_2O_3^{2-}$

$= \frac{1}{2} * \frac{15}{1000} * 0.0510 =0.000383 \ mol$

Note: The division by 1000 is to convert mill liter to liter

Moles of ascorbic acid = moles of $I^{3-}$ reacted

$= initial \ moles \ of \ I^{3-} \ - remaining \ moles \ of \ I^{3-}$

$=0.000784 - 0.000383$

$=0.000401 \ mols$

$Mass = moles \ * molar \ mass$

Hence

Mass of ascorbic acid = moles of ascorbic acid × molar mass of ascorbic acid

$= 0.000401* 176.12 = 0.07055\ g$

$= 70.55\ mg$

Weight% of ascorbic acid = mass of ascorbic acid/mass of sample x 100%

= 70.55/80 × 100%

= 88.1%

3 0

4 years ago

Which postmortem parameter is fixed by 8 hours?

lara [203]

Answer:

Algor mortis is the change which is an immediately sign of death. It involves the cooling of body. The body temperature decreases as the body after death looses the control over the circulation and exchange of gases and the control over the homeostasis. The temperature decreases until the body attains equilibrium with the external environmental temperature. The postmortem cooling or algor mortis gets fixed by 8- 10 hours after death. The temperature of the body after death can be used to determine the time since death. This can be measured by determining the temperature of the rectum which is proved to be most accurate or any other orifice such as nasal, ear and vaginal can also be used.

4 0

3 years ago

A student went to the dentist and found out that he had a cavity. He always brushes his teeth twice a day, so he didn't understa

Free_Kalibri [48]

Answer:

The drinks that the student should avoid - if he wants to avoid damage to his teeth - are drinks C and E, since they are acidic, according to their pH.

Explanation:

pH measures the acidity or alkalinity of a solution, taking into account the amount of hydrogen ions present in it, and established on a scale that goes from 0 to 14.

In chemistry, pH is derived from the formula that indicates:

pH = - Log₁₀ αH⁺ , where α is the activity of hydrogen ions.

A solution with a pH of 7 is considered neutral, above this value it is an acidic solution and below this value it is called acidic.

According to this:

Acidic drinks are: drink C (5.3) and E (2.4).
The basic drinks are: drink A (11.9) and drink D (9.8).
The neutral drink is the drink B (7), which corresponds to water.

4 0

3 years ago