Ions move in the direction opposite to that favored by the chemical concentration gradient when
a. potassium ions exit the neuron during the repolarization phase of an action potential
b. they are pumped by proteins that require atp hydrolysis and when the electrical charge gradient repulses or attracts them
c. simple diffusion operates after active transport has been permanently halted by being poisoned proteins leak out of a neuron
d. sodium ions enter a neuron during the depolarization phase of an action potential

B. they are pumped by proteins that require ATP hydrolysis and when the electrical charge gradient repulses or attracts them

Explanation:

Hello,

Ions move in the direction opposite to that favored by the chemical concentration gradient when they are pumped by proteins that require ATP hydrolysis and when the electrical charge gradient repulses or attracts them because active pumping moves ions against their chemical concentration gradients and the Nernst equation describes how membrane potentials can yield electrical gradients to motivate ion movement.

Best regards.

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol