Question

Chemistry! Help! Please!

Answer 1

Question 1

The correct answer is a.

Explanation

The relationship between $pH$ and $pOH$ is given by

$pH + pOH = 14$, We can use $pH=-log[H^+]$ and $pOH= -log[OH^-]$. In a we are given the concentration of [OH] and so we use that to find the pOH, then from pOH we can find the pH.

$pOH= -log [2.4 \times 10^-^2] = 1.62\\\\pH = 14 - 1.62= 12.38$

$b.pH=-log(1.53 \times 10^-^2) = 1.82$

c. HCl is a strong acid so it dissociates to 0.0001 $H^+$ and 0.0001 $Cl^-$, hence

$pH= -log[0.0001] = 4$

$d.pOH= -log [4.4 \times 10^-9] = 8.36\\\\pH= 14- 8.36 = 5.64$

$a.[OH^-] = 2.4 \times 10^-^2$ has a pH 12.36 which is greater than 7

Question 2

The correct answer is d $O_2(g)$.

Explanation

This is because solids and liquids do not appear in the equilibrium constant expression. Since $K= \frac{[products]}{[reactants]}$.

For the equation

$2PbS_(_s_) + 3O_2_(_g_) + C_(_s_) \implies 2Pb _(_s_) + CO_2_(_g_) + SO_2(_g_)$

$K= \frac{[CO_2][SO_2]}{[O_2]}$

Question 3

The correct answer is c

In a molecule the oxidation number are assigned to get the sum of a neutral charge or ion. The overall charge of $SO_4^2^-$ is -2 and in all its compounds oxygen has -2 charge, hence

$S+ 4O = -2\\S+4(-2)=-2\\\implies S= -2 +8 = +6$

Question 4

The correct answer is b. An oxidising agent must gain electrons in a reaction, thus it is the one that undergoes reduction.In order find out what is being reduced we write half reactions for molecules that change their state. $Ag^+$ and $K^+$ are spectactor ions in this reaction.

$Cl_2 + 2e \implies 2Cl^-\\\\NO_2 +H_2O \implies NO_3 +2H^+ +2e\\\\H^+ + OH^- \implies H_2O$

In the chloride half reaction $Cl_2$ gains electrons to become $Cl^-$ ions.

Question 5

The last element D is correct. When a nucleus decays by beta emission it produces a daughter nucleus that has same mass number but different atomic number. Therefore beta-decay will have equation

$\frac{187}{75} Re \implies \frac{187}{76} Os + \beta$

Question 6

The correct answer is a. A beta particle is an electron because it has a charge of -1 and has same mass as an electron, while a positron is  a particle with the same mass as an electron  but with a positive charge.