17. Which of the following represent the correct net ionic equations from the double replacement reaction of calcium nitrate and potassium phosphate?
a. Caaq) + PO43- (aq) → CaPO4(s)
b. Q Ca2+ (aq) + 3 PO43- (aq) → Caz(PO4)3(S)
c. 3 Ca2+ (aq) + 2 PO.3(aq) → Caz(PO4)2(S)
d. 2 NO3(aq) + Ca2+
+ Ca(NO3)2(S)

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.