Answer: e) 9.43
Explanation: A buffer solution is a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid and the pH of the buffer is calculated using Handerson equation:
There are 25 mL of 0.50 M which is a weak base. 25 mL of 0.20 M HCl, a strong acid are added. Ammonia reacts with HCl to form its conjugate acid, ammonium ion. The net ionic equation will be:
From above reaction, ammonia and HCl react in 1:1 mol ratio. Let's calculate the moles of each we have before the reaction. There is also, 1:1 mol ratio between HCl and ammonium ion.
moles of ammonia =
= 0.0125 mol
moles of HCl =
= 0.005 mol
Excess moles of ammonia = 0.0125 - 0.005 = 0.0075 mol
moles of ammonium ion formed = 0.005 mol
Total volume of the solution = 0.025 mL + 0.025 mL = 0.050 L
concentration of ammonia in buffer =
= 0.15 M
concentration of ammonium ion in buffer =
= 0.10 M
pKa is calculated from given Ka as:
pKa = 9.25
Plug in the values in Handerson equation:
pH = 9.25 + 0.18
pH = 9.43
So, the correct choice is e) 9.43 .
MgSO₄ + Pb(NO₃)₂ = PbSO₄(s) + Mg(NO₃)₂
Mg²⁺ + SO₄²⁻ + Pb²⁺ + 2NO₃⁻ = PbSO₄ + Mg²⁺ 2NO₃⁻
Pb²⁺ + SO₄²⁻ = PbSO₄
Answer: option C - The cells produced at the end of meiosis contain half the number of chromosomes as the parent cell
Explanation:
Meiosis is also known as REDUCTIVE DIVISION, simply because a parent cell with diploid number of chromosome (46) is divided into four daughter cells with haploid number of chromosome (23)
Thus, ONLY option C correctly defines meiosis
Answer:
This question is incomplete
Explanation:
This question is incomplete. However, there are ways to save the forest of third world countries - this includes
1) Creating of forest reserves: Wide areas of land that are still forested can still be preserved and converted to forest reserves which can prevent these areas from being deforested as a result of human activities or industrialization.
2) Government policies: Government can put policies in place to prevent people from embarking on deforestation of certain lands. This is because some parts of the third world countries still rely on wood for cooking and other sources of daily activities.
3) Replanting of deforested areas: Replanting of trees can also help third world countries in saving the forest.