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2 years ago

3. The opening that allows light to enter the eye is the

Chemistry

2 answers:

AlexFokin [52]2 years ago

5 0

Answer:

A. The opening that allows light to enter the eye is the iris.

Explanation:

xxMikexx [17]2 years ago

4 0

Answer:

A) Iris

Explanation:

The Iris controls the diameter of the opening in your eye, thus also controlling the amount of light let inside. It's also reponsible for the colour of you eye.

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A chemist prepares hydrogen fluoride by means of the following reaction:

natita [175]

Answer:

39.3%

Explanation:

CaF2 + H2SO4 --> CaSO4 + 2HF

We must first determine the limiting reactant, the limiting reactant is the reactant that yields the least number of moles of products. The question explicitly says that H2SO4 is in excess so CaF2 is the limiting reactant hence:

For CaF2;

Number of moles reacted= mass/molar mass

Molar mass of CaF2= 78.07 g/mol

Number of moles reacted= 11g/78.07 g/mol = 0.14 moles of Calcium flouride

Since 1 mole of calcium fluoride yields two moles of 2 moles hydrogen fluoride

0.14 moles of calcium fluoride will yield 0.14×2= 0.28 moles of hydrogen fluoride

Mass of hydrogen fluoride formed (theoretical yield) = number of moles× molar mass

Molar mass of hydrogen fluoride= 20.01 g/mol

Mass of HF= 0.28 moles × 20.01 g/mol= 5.6 g ( theoretical yield of HF)

Actual yield of HF was given in the question as 2.2g

% yield of HF= actual yield/ theoretical yield ×100

%yield of HF= 2.2/5.6 ×100

% yield of HF= 39.3%

4 0

3 years ago

the first three ionization energies of an element x are 590, 1145, and 4912 kj mol-1. what is the most likely formula of the com

joja [24]

Answer: The chemical formula is $XSO_3$

Explanation:

Ionization energy is defined as the amount of energy that is required to remove an electron from a chemical species.

The ionization energy equation for the given values follow:

$X(g)\rightarrow X^+(g)+e^-;E_I=590kJ/mol$

$X^+(g)\rightarrow X^{2+}(g)+e^-;E_I=1145kJ/mol$

$X^{2+}(g)\rightarrow X^{3+}(g)+e^-;E_I=4912kJ/mol$

From the values of ionization energy above, it can be seen that the ionization energy increases as every succeeding electron is removed.

Second ionization energy is a little higher than the first one but there is a huge amount of difference between the third and second ionization energy.

This implies that the ion formed during second ionization energy has a stable configuration and it requires a humongous amount of heat to release the third electron.

Hence, the ion formed will be $X^{2+}$

Sulfite ion is a polyatomic ion having a chemical formula of $SO_3^{2-}$

An ionic compound is formed between the two ions and the chemical compound formed between the two will have a formula of $XSO_3$

Hence, the chemical formula is $XSO_3$

5 0

2 years ago

Which of these pairs of elements have the same number of valence electrons?

Taya2010 [7]

The same number of valence electrons exists in the same family of elements in the periodic table. In finding the answer to this problem, we just have to find the pair that belongs to the same family in the periodic table. The same family means same column. Among these, Oxygen and lead (Pb) are in the same family. This pair is the answer.

7 0

3 years ago

Calculate the solubility of hydrogen in water at an atmospheric pressure of 0.380 atm (a typical value at high altitude).

Pani-rosa [81]

The question is incomplete, here is the complete question:

Calculate the solubility of hydrogen in water at an atmospheric pressure of 0.380 atm (a typical value at high altitude).

Atmospheric Gas Mole Fraction kH mol/(L*atm)

$N_2$ $7.81\times 10^{-1}$ $6.70\times 10^{-4}$