First we need to find the number of moles that 43.9g of gallium metal is. We can do this by finding the molar weight of gallium and cross-multiplying to cancel out units:

So we are dealing with 0.63 moles of gallium metal.
We can take from the balanced equation that 4 moles of gallium metal will react completely with 3 moles of oxygen gas. We can take this ratio and make a proportion to find the amount of oxygen gas, in moles, that will react completely with 0.63 moles of gallium metal:

Cross multiply and solve for x:
4x=1.89
x=47 molesO₂
So now we know that 0.47 moles of oxygen gas will react with 43.9g of gallium metal.
The answer is C. Aluminium since it is highly reactive
Meteorites, I think it’s an asteroid when in space and a meteorite once it lands
Explanation:
For the given equation:
NH3 + HCl -> NH4Cl
This is an acid-base reaction (neutralization): NH3 is a base, HCl is an acid and NH4Cl is the sal.
Answer: b) NH3 is the base and NH4CI is the salt.
For the reaction to take place the energy of the reactants must reach to the energy level of the products:
we have 900 J in the reactants and 9000 J for the products so the reactants need 8100 J to reach to the value of energy of products (900 + 8100 = 9000)
So the correct answer is C. <span>The reaction absorbs 8100 J of energy from the surroundings as it proceeds. </span>