An atom has a mass number of 25 and 13 neutrons. what is the atomic number of this atom? express your answer as an integer.

Urea, co(nh2)2, is manufactured on a large scale for use in producing urea-formaldehyde plastics and as a fertilizer. what is the maximum mass of urea that can be manufactured from the co2 produced by combustion of 1.00 x 104 grams of co2?

Iknow #2 is d. i just need to know why

1. suppose a reaction mixture, when diluted with water, afforded 300 ml of an aqueous solution of 30 g of the reaction product malononitrile [ch2(cn)2], which is to be isolated by extraction with ether. the solubility of malononitrile in ether at room temperature is 20.0 g/100 ml, and in water is 13.3 g/100 ml. what weight of malononitrile would be recovered by extraction with (a) three 100-ml portions of ether and (b) one 300-ml portion of ether? suggestion: for each extraction, let x equal the weight extracted into the ether layer. in part (a), the concentration in the ether layer is x/100 and in the water layer is (30 x)/300; the ratio of these quantities is equal to k 20/13.3.