BMAT Prep Question Analysis Q170 & Q100
Q170 In a science experiment, a student measures a set amount of calcium carbonate with hydrochloric acid, producing carbon dioxide gas: CaC03(s) + 2HCI(aq) -> CaCI2(aq) + H20(1) + CO2(g).
The rate of this reaction can be measured using the apparatus shown here.
Which additional piece of equipmentnis needed to find out the rate of reaction shown by the equation above?
a. A clock
b. A burette
c. A thermometer
d. A condensation funnel
Q100 If the sun were to disappear suddenly at once, what would be the effect of its disappearance on the orbit of the Earth?
a. The orbit would remain unchanged, due to the absence of an external force
b. The orbit would slowly decay until the Earth was stationary
c. The Earth would immediately become stationary
d. The Earth would move in a straight line tangential to its previous orbit
e. The Earth would fall toward the sun's former position
f. The Earth would accelerate into space
Answer and Explanation
Q170 Answer: a. A clock
Explanation: A clock is needed to work out the rate of reaction i.e. how fast a reaction occurs. This can be calculated when the reaction is fully completed and no further reduction in weight is seen on the scale (as the equation is only in one direction). A burette is a graduated glass tube with a tap at one end used for delivering known volumes of a liquid, especially in titrations; as such it would add any value. We do not need to know the temperature, nor are we collecting the carbon dioxide product; hence neither the thermometer nor the condensation funnel are relevant.
Q100 Answer: d. The Earth would move in a straight line tangential to its previous orbit
Explanation: The disappearance of the sun would remove the force keeping the Earth in an elliptical orbit. Orbital mechanics is quite a complicated branch of mathematics, but the solution to this question is entirely based in Newton's First law; in the absence of the force of the sun's gravitational pull, the Earth's speed would remain constant but the direction would no longer change, resulting in a continuous motion along a straight line into space.
Imagine a rock on the end of a string. If you were to swing it in circles about one's head and then release it, it would fly off in a straight line.
Drafted by Quincy (BMAT Prep)