$$ 7.00 \ text {mol (nh} _4) _2 \ text {s} \ times \ frac {8 \ text {mol h}} {1 \ text {mol (nh} _4) \ text {s}} =\ boxed {56 \ text}} $$
$$ 7.00 \ text {mol (nh} _4) _2 \ text {s} \ times \ frac {8 \ text {mol h}} {1 \ text {mol (nh} _4) \ text {s}} =\ boxed {56 \ text}} $$