Answer:
Example
0.5 mol of sodium hydroxide is dissolved in 2 dm3 of water. Calculate the concentration of the sodium hydroxide solution formed.
Concentration =
Concentration = 0.25 mol/dm3
Volume units
Volumes used in concentration calculations must be in dm3, not in cm3. It is useful to know that 1 dm3 = 1000 cm3. This means:
divide by 1000 to convert from cm3 to dm3
multiply by 1000 to convert from dm3 to cm3
For example, 250 cm3 is 0.25 dm3 (250 ÷ 1000). It is often easiest to convert from cm3 to dm3 before continuing with a concentration calculation.
Question
100 cm3 of dilute hydrochloric acid contains 0.02 mol of dissolved hydrogen chloride. Calculate the concentration of the acid in mol/dm3.
Reveal answer
Converting between units
The relative formula mass of the solute is used to convert between mol/dm3 and g/dm3:
to convert from mol/dm3 to g/dm3, multiply by the relative formula mass
to convert from g/dm3 to mol/dm3, divide by the relative formula mass
Remember: the molar mass is the Ar or Mr in grams per mol.
Example
Calculate the concentration of 0.1 mol/dm3 sodium hydroxide solution in g/dm3. (Mr of NaOH = 40)
Concentration = 0.1 × 40
= 4 g/dm3
Answer:
There are necessaries 35,2g of NH₄NO₃ per 100,0g of water to decrease the temperature of the solution from 25,0°C to 5,0°C
Explanation:
To decrease the temperature of the solution there are necessaries:
4,184J/g°C×(5,0°C-25,0°C)×(100,0g+X) = -Y
8368J + 83,68J/gX = Y <em>(1)</em>
Where x are grams of NH₄NO₃ you need to add and Y is the energy that you need to decrease the heat.
Also, the energy Y will be:
Y = 25700J/mol×
X
Y = 321J/g X <em>(2)</em>
Replacing (2) in (1)
8368J + 83,68J/g X = 321J/g X
8363J = 237,32J/gX
<em>X = 35,2g</em>
<em />
Thus, there are necessaries 35,2g of NH₄NO₃ per 100,0g of water to decrease the temperature of the solution from 25,0°C to 5,0°C
I hope it helps!
Look up chromium on periodic table.
It's atomic number is 24.
It gives number of protons in an element.
Since the atom is uncharged (no extra or subtracted electrons), the number of protons will equal the number of electrons.
Answer:
See the answer below
Explanation:
Even though plants are rooted in the ground, they still move, exert <u>force,</u> and do<u> work</u>.
Plant cells have very strong cell walls that allow <u>pressure</u> to build up inside of the cell as water is absorbed. This pressure is called <u>turgor</u>.
When turgor pressure is high enough in a cell, the cell walls become <u>firm</u> and as a result, the cell becomes rigid and the plant is able to stand <u>tall</u> and<u> straight</u>.
When a plant does not get enough water, the turgor pressure inside of the cells <u>decreases.</u> A decrease in <u>pressure</u> pushing against the cell wall causes the cells to lose their <u>shape</u> and <u>shrink</u>. This causes the plant to begin to droop or <u>wilt</u>.
When the wilted plant gets enough water, the cells will become rigid again, and the plant will stand firm and straight once again.
