What properties change the compisition of a substance a) chemical properties b)physical properties c) both chemical and physical d) neither chemical or physical 2: what option is an example of a physical change a)boiling point b) ph c)toxicity d)rusting ability 3) same question ^ a) flammibility b)ph c)toxicity d)freezing point 4) what is an example of a chemical property a)boiling point b) color c)reactivity d) density 5) same question ^ a)reactivity b)color c) melting point d)density

1. a) chemical properties.

2. a) boiling point.

3. d) freezing point.

4. c) reactivity.

5. a) reactivity.

EXPLANATION:

A physical change is one in which there is no change in composition of substance, however chemical change is one in which there is change in composition of substance. By composition we mean what molecules the substance is made up of. see the pics to understand more.

in boiling, freezing or melting, the substance just changes from solid to liquid or liquid to solid or liquid to gas but there is no change in composition.

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

the answer is d. 74.02