Gas equation help!!!!!!

Need help for test next week.

1.A mixture of N2 and Zn (s) in a flask at 23.0 C exerts a pressure of 555 torr. 5.34 g of CO2 is added and the pressure is now 666 torr (temp remains constant). How many g of N2 are present?

2.A piece of Ca metal undergoes a complete reaction with H2O(L) to produce calcium hydroxide and hydrogen. When 3.30 g of Ca in a 2.00 L container is reacted with an excess amount of water at 35.0 C, the final pressure in the 2.00 L container is 2.22 atm when the reaction is completed. (The vapor pressure of H2O at 35 C= 23.8 mm Hg). What was the initial pressure in the 2.00 L container before the Ca was added?

1) for gases, partial pressure is directly related to the mole ratio of the gases. If there is 80% of a certain gas in a sample, then it will make up 80% of the pressure. So CO2 has a molecular weight of 44g. 5.34g/44g is .121moles of CO2 present. CO2's pressure here is 666torr after CO2 is added minus the initial 555torr from nitrogen. So 666-555 is 111. 111/666 is 16.7%, which is the percent pressure that the CO2 is exerting. Since the ratio of pressures must also equal the ratios of moles, .121/(moles of N2)= .167. Moles of N2 are .725. The molecular weight of N2 is 14g /mole. So .725X14 is 10.15g of N2.

2) The only thing creating pressure before the reaction happens is the vapor pressure of water which is stated at 23.8mm Hg.