Are these two correct ?

According to the law of conservation of mass, in a chemical reaction the total starting mass of all the reactants equal the total final mass of all the products. true or false?

Aboy with a mass 25 kg climbs into a small tree. he sits on a branch that is 2.o m above to the ground.what is his gravitational potential energy above the ground?

Consider each of the electric- and magnetic-field orientations given next. in each case, what is the direction of propagation of the wave? a)\vec ein the +xdirection,\vec bin the +ydirection. choose+ x direction- x direction+ y direction- y direction+ z direction- z direction b)\vec ein the -y direction,\vec bin the +x choose+ x direction- x direction+ y direction- y direction+ z direction- z direction c)\vec ein the +z direction,\vec bin the -x direction. choose+ x direction- x direction+ y direction- y direction+ z direction- z direction d)\vec ein the +y direction,\vec bin the -z direction. choose+ x direction- x direction+ y direction- y direction+ z direction- z direction