This is true! Heterozygous would be Dd, and the dominant masks the recessive
Answer:
- <em><u>Mendeleev produced the first orderly arrangement of known elements.</u></em>
- <em><u>Mendeleev used patterns to predict undiscovered elements.</u></em>
Explanation:
- <u>Mendeleev produced the first orderly arrangement of known elements and used patterns to predict the undiscovered elements.</u>
Those two statments are true.
For the time being there were some 62 known elements. Before Medeleev some schemes to order part of the elements were proposed, but Medeleev showed the relationship between the atomic mass and the properties of the elements (supports second choice). This arrangement is known as the periodic table.
More importantly, Mendeleev predicted correctly the existance and properties of unknown elements, which is his major contribution: he left blanket spaces which where gradually filled when new elements where discovered (this supports the fourth choice).
The first modern chemistry book was written by Antoine Lavoisier (this discards first option).
Mendeleev ordered the elements by increasing mass number (this discards third choice), which was corrected later by the scientist Henry Moseley, who ordered the elements by increasing atomic number (number of protons).
Isotopes were not known by Mendeleev times, so this discards the last option.
It is limited by the depth divers and equipment can go.
Answer:
6e⁻
Explanation:
Charge in reducing 2 mole of Cr⁶⁺ to Cr³⁺
Cr⁶⁺ + xe⁻ → Cr³⁺
The numbers 6+ and 3+ on the chromium atoms are the oxidation number of the atom.
It shows the number of electrons that has been lost by chromium in an oxidation state.
Cr⁶⁺ shows that it has lost 6 electrons. When an atom loses electrons, the number of protons becomes more. This makes it positively charged in nature.
This analogy goes for Cr³⁺
Therefore, in going from reactants to products, chromium
6+ → 3+
In this kind of expression, the number of atoms must be conserved and the charges too;
2Cr⁶⁺ + xe⁻ → 2Cr³⁺
given 2 moles of Cr;
To balance the charge;
2(6+) + x(-) = 2(3+)
12 - x = 6
x = 6
A charge of 6e⁻ is required to reduce 2 mole of Cr⁶⁺ to Cr³⁺
