How many joules are needed to change the temperature of 100. g of water from 20 to 45

This can be found by using Q=mcΔt, where Q is the heat in joules, m is mass in grams, c is the specific heat, and Δt is the change in temperature (final-initial)
So,
Q= (100.g)(4.18J/g°C)(15°C)
Q= 6897J needed

1. o2(g)as a product