6th grade science i mark as brainliest

Which of the following is always a reactant in a combustion reaction? oxygen nitrogen hydrogen carbon

7. what temperature is need to just dissolve 50 g of nh4cl in 75 g of water? '

Sally is making a model of a magnesium atom with an atomic mass number of 24 for her chemistry class. she has foam balls for the protons, neutrons, and electrons. she has added 6 neutrons to her model so far. how many more neutrons does she need to add to complete her neutral atom of magnesium?