HCN(aq) + H20 (1) 3 H30+ (aq) + CN- (aq) Ka = H30+][CN"] – 62 x 10-10 [HCM] The equilibrium reaction shown above represents the partial ionization of the weak acid HCN (aq). A 0.200 M HCN (aq) solution has a pH ~ 4.95. If 0.05 g (0.010 mol) of NaCN (s) is added to 100 mL of 0.200 M HCN (aq), which of the following explains how and why the pH of the solution changes? a The pH will be higher than 4.95 because adding CN- will disrupt the equilibrium, resulting in an increased production of HCN that decreases the concentration of H3O+. c will disrupt the equilibrium, resulting in an increased production of HCN that decreases the concentration of ) The pH will be lower than 4.95 because adding CN H30+. c) The pH will be higher than 4.95 because CN is a strong base that can neutralize HCN. ( D ) The pH will remain close to 4.95 because the K, is so small that hardly any products form.

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol

every chemical equation adheres to the law of conservation of mass, which states that matter cannot be created or destroyed. therefore, there must be the same number of atoms of each element on each side of a chemical equation.