In the chemical reaction below, calcium (Ca) and water (H2O) react to form calcium hydroxide (Ca(OH)2) and hydrogen gas (H2). Ca() + 2H2O() → Ca(OH)2() + H2() Calcium and water are the reactants in this chemical reaction. The products are calcium hydroxide and hydrogen gas. Which statement correctly describes the total mass of the products when the reaction is complete?
A. The total mass of the products will be greater than the original mass of the reactants.
B. The total mass of the products will be less than the original mass of the reactants.
C. The total mass of the products will be equal to the original mass of the reactants.
D. The total mass of the products cannot be found from the original mass of the reactants.

C.

Explanation:

The mass of the reactants should not change, in fact it would be equal because the only thing that changes is the form in which your products are in. The reactants will still have the same amount of mass from the products as no products were removed or added, the structure changed, the mass did not.

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol