Answer:
Energy is needed by all organisms for cell and life processes
Explanation:
Energy is needed for all life processes. This energy comes from outside the body of the individual organism.
Answer:
7.98 g of glucose are needed to prepare 399 mL of glucose solution
Explanation:
2.0 % m/v
This data represents, a sort of concentration for solutions.
It means that, our solution contains 2 g of solute, in this case glucose, which are contained by 100 mL of solution.
We only have to make a rule of three, in order to solve the question:
In 100 mL of glucose solution, we have 2 g of solute
In 399 mL of glucose solution, we may have:
(399 . 2) / 100 = 7.98 g
<span>0.0165 m
The balanced equation for the reaction is
AgNO3 + MgCl2 ==> AgCl + Mg(NO3)2
So it's obvious that for each Mg ion, you'll get 1 AgCl molecule as a product. Now calculate the molar mass of AgCl, starting with looking up the atomic weights.
Atomic weight silver = 107.8682
Atomic weight chlorine = 35.453
Molar mass AgCl = 107.8682 + 35.453 = 143.3212 g/mol
Now how many moles were produced?
0.1183 g / 143.3212 g/mol = 0.000825419 mol
So we had 0.000825419 moles of MgCl2 in the sample of 50.0 ml. Since concentration is defined as moles per liter, do the division.
0.000825419 / 0.0500 = 0.016508374 mol/L = 0.016508374 m
Rounding to 3 significant figures gives 0.0165 m</span>
2.48 grams.
<h3>Explanation</h3>
Start by finding the formula mass for cobalt (II) chloride and cobalt (II) chloride hexahydrate.
As a transition element in the middle d-block of the periodic table, cobalt can form ions with a plurality of charges. It is thus necessary to indicate its charge in systematic names of cobalt-containing formula.
The cation "cobalt" in the systematic name of the salt has the Roman numeral "(II)" attached to it in brackets. As a metal, cobalt forms positively-charged ion. The one here thu has charge of +2.
Chloride ions have charges -1. Charges cancel out to produce neutral compounds. Each cobalt cation in this salt would thus pair with two chloride anions. Hence the empirical formula: .
The prefix "<em>hexa-</em>" in the name cobalt (II) chloride <em>hexa</em>hydrate indicates that every formula unit of this salt contains six units of water. The hydrated salt thus has an empirical formula of .
Given the relative atomic mass for each of the elements, as seen on a modern periodic table of the elements:
- Cobalt- 58.93
- Chloride- 35.45
- Hydrogen- 1.008
- Oxygen- 16.00
Thus the formula mass of each compound
- Cobalt (II) chloride - 129.83
- Cobalt (II) chloride hexahydrate - 262.12
Cobalt (II) chloride hexahydrate decomposes under heat to produce cobalt (II) hexahydrate and water. Hence the equation:
Therefore
- Molar ratio:
- Mass ratio:
The mass ratio indicates that 262.12 grams of cobalt (II) chloride hexahydrate decomposes to produce 129.83 grams of its corresponding anhydrous salt. Accordingly, heating 5.00 grams of the hexahydrate would produce 2.48 grams of its anhydrate.