Answer:
5.61 * 10²¹ molecules
Explanation:
You have 1.25 g of malic acid, C4H.Os, an acid found in apples and other fruits. How many molecules of the acid do you have?
Solution:
A molecule is the group of two or more atoms held together by chemical bonds.
The number of molecules is calculated using the formula:
number of molecules in a substance = number of moles of substance * Avogadro constant
Avogadro constant = 6.02 * 10²³ mol⁻¹
number of moles = mass / molar mass
Given that mass = 1.25 g
molar mass of malic acid (C₄H₆O₅) = (12 * 4) + (1 * 6) + (16 * 5) = 48 + 6 + 80 = 134 g/mol
number of moles = mass / molar mass = 1.25 g / 134 g/mol = 0.0093 mol
Recall that: number of molecules in a substance = number of moles of substance * Avogadro constant
number of molecules in a substance = 0.0093 mol * 6.02 * 10²³ mol⁻¹ = 5.61 * 10²¹ molecules
Answer:
pH =3.8
Explanation:
Lets call the monoprotic weak acid HA, the dissociation equilibria in water will be:
HA + H₂O ⇄ H₃O⁺ + A⁻ with Ka = [ H₃O⁺] x [A⁻]/ [HA]
The pH is the negative log of the H₃O⁺ concentration, we know the equilibrium constant, Ka and the original acid concentration. So we will need to find the [H₃O⁺] to solve this question.
In order to do that lets set up the ICE table helper which accounts for the species at equilibrium:
HA H₃O⁺ A⁻
Initial, M 0.40 0 0
Change , M -x +x +x
Equilibrium, M 0.40 - x x x
Lets express these concentrations in terms of the equilibrium constant:
Ka = x² / (0.40 - x )
Now the equilibrium constant is so small ( very little dissociation of HA ) that is safe to approximate 0.40 - x to 0.40,
7.3 x 10⁻⁶ = x² / 0.40 ⇒ x = √( 7.3 x 10⁻⁶ x 0.40 ) = 1.71 x 10⁻³
[H₃O⁺] = 1.71 x 10⁻³
Indeed 1.71 x 10⁻³ is small compared to 0.40 (0.4 %). To be a good approximation our value should be less or equal to 5 %.
pH = - log ( 1.71 x 10⁻³ ) = 3.8
Note: when the aprroximation is greater than 5 % we will need to solve the resulting quadratic equation.
When a solid is heated , the average kinetic e energy of the substance increases because of which the temperature increases....this heat won’t affect the average kinetic energy of the substance. Since average kinetic energy will remain same during phase change , the temperature will remain same too.
***HOPE THIS HELP YOU***
Answer: here is your answer
Explanation:
The oxygen family consists of the elements that make up group 16 on the periodic table: oxygen, sulfur, selenium, tellurium, and polonium. These elements all have six electrons in their outermost energy level, accounting for some common chemical properties among them.
Answer:
0.31 g
Explanation:
The equation of the reaction;
HKC8H4O4(aq) + NaOH(aq) ----> Na(KC8H4O4)(aq) + H2O(l)
Number of moles of NaOH = 15/1000 L × 0.1 M
= 0.0015 moles
Since the reaction is 1:1, 0.0015 moles of KHP reacted;
Number of moles of KHP = mass of KHP reacted/molar mass of KHP
Mass of KHP = Number of moles of KHP × molar mass of KHP
Mass of KHP = 0.0015 moles × 204.22 g/mol
Mass of KHP = 0.31 g
