It depends on the sand itself, if it contains silt ( mud), or it contains sulfates , both will crack the mortar , usually in Iraq its one part of cement to 2.25 parts of sand in middle and south of...
not a lot. but assuming 9"x3" and using this brick calculator
it works out at 0.0003 cubic meters of mortar or 0.91kg of sand and 0.25kg of cement per brick.
It depends on the age of the mortar.
Today's mortar is made from sand, Portland cement and water. In very cold weather a plasticiser is added.
Prior to about 1900 mortar was made from sand, lime...