My findings are written from the New world translation ,and in our own language this is what they both mean.
“By grace [“undeserved kindness,” NW] you have been saved through faith; and this is not your own doing, it is the gift of God—not because of works, lest any man should boast.” ... (The entire provision for salvation is an expression of God’s undeserved kindness.
Mercy is an expression of kind consideration or pity that brings relief to those who are disadvantaged.
(2 Corinthians 1:3) Mercy is shown by treating someone in a compassionate way. ... This is a major facet of God’s personality.