The concentration of OH- ( symbol: [OH-] ), is equal to 10^-pOH (ten to the pOH'th power). The pOH equals 14 minus the pH, because the pH + the pOH = 14. So the pOH is 14-13= 1. Now the concentration of OH- is 10^-1 (= 1) moles/Litre
<span>NaOH (s) --> Na+ (aq) + OH- (aq) </span>
<span>1. : 1. : 1 </span>
<span>So by dissolving one mole of NaOH, you get one mole of Na+ and one mole of OH-. Meaning that the molarity (number of solved NaOH in one Litre) of NaOH is 1 mole/Litre, because the ratio is 1:1. This means, in ten litres of water there are also ten moles of NaOH. And the weight of one mole of NaOH is 40.00 grams (look it up in literature). So in ten litres solution with a pH of 13, there are 40.00*10 = 400 = 4 * 10^2 grams of NaOH dissolved</span>
Answer:
127K
Explanation:
Recall that the density of a gas (ρ) is related to the molar mass of the gas (M), the ideal gas constant (R), and the temperature in Kelvin (T). This relationship is described by the equation below.
ρ=PMRT
We are asked to solve for the temperature at which neon gas, Ne(g), will have a density of ρ=1.45gL. Rearrange the equation above to solve for T and substitute the given values into the equation.
ρT=PMRT=PMRρ=(0.750atm)(20.180gmol)(0.08206L atmmol K)(1.45gL)=127.2K
Therefore, after rounding to three significant figures, we find that the temperature is approximately 127K.
Answer:
Option (d) is correct
N³⁻ > F⁻ > Mg²⁺ > Si⁴⁺
Explanation:
Total electrons for all the species = 10
So these are <u>iso electronic</u> with each other.
We know
Ionic radii ∝ 
- Si⁴⁺ has 14 protons and 10 electrons
- Mg²⁺ has 12 protons and 10 electrons
- N³⁻ has 7 protons and 10 electrons
- F⁻ has 9 protons and 10 electrons
- Iso electronic species with greatest number of protons have small size and vice versa.
- So Si⁺⁴ have smallest size and N³⁻ have largest in size
Answer:
Always carry the microscope with two hands. One on the arm and one underneath the base of the microscope.
Answer:
The correct choices are:
- <em>using accurate measurements</em>
- <em>using pure chemicals</em>
- <em>performing the reaction under the most ideal conditions</em>
Explanation:
The theoretical yield is the maximum amount of product that could be obtained by the chemical reaction, from a given amount of reactants. You calculate the theoretical yield using the stoichiometry coefficients of the balanced chemical equation.
The <em>percent yield </em>is the ratio of the actual yield (the actual amount obtained) of a product to the theoretical yield for the same product, expressed as a percentage (i.e. multiplied by 100).
- percent yield = actual yield × 100 / theoretical yield
As the actual yield decrease (the numerator of the ratio), the percent yield decrease.
To increase the percent yield it is important:
- using accurate measurements
- performing the reaction under the most ideal conditions
<em><u>Using accurate measurements:</u></em> if you do not add the correct amounts of each reactant, then the product obtained will not be what you can predict from the theoretical calculations and you will be wasteing one or other reactant, without reaching the maximum yield possible.
<em><u>Using pure chemicals:</u></em> if the chemicals are not pure, the amount of actual reactants will be lower than they should be, leading to a lower actual yield.
<em><u>Performing the reaction under the most ideal conditions:</u></em> the actual rate of reactions depend on the conditions: temperature and pressure are the most commons. Since, temperature and pressure may change that rate of reactions, you should find and use the most ideal conditions to get the greatest actual yield.
<em>Adding water</em>, can just dilute the reactants and would decrease the rate of reaction, which would not be helpful to increase the yield.
