Begin by writing formulas for the reactants and products, including physical states. When necessary use coefficients to balance the equation. Click in the answer box to open the symbol palette.

(a) When solid sodium hydride, NaH, is added to water, hydrogen gas is released and aqueous sodium hydroxide forms.

AP 1

(b) Aluminum metal reacts with chlorine gas to form solid aluminum chloride.

NaH(s) + H2O(l) > NaOH(aq) + H2(g)

2Al(s) + 3Cl2(g) > 2AlCl3(s)

Explanation:

The rule of thumb in balancing chemical reaction equation is that the number of atoms of each element on the reactant side must be the same as the number of atoms of the same element on the product side. Only then can any reaction equation be seen as balanced.

For example there are two aluminum atoms on both sides of the reaction equation and six chlorine atoms on both sides of the reaction equation. Hence the reaction equation is balanced.

what is the average time it took the car to travel 0.25 meters?

⇒ 2.23 seconds

what is the average time it took the car to travel 0.50 meters?

⇒ 3.13 seconds

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.