When chemists write out reactions, they often place numbers to the left of a chemical formula. e. g. the first 2 in: 2h+> h2o, what do you call these numbers to the left of chemical formulas? coefficients, subscript numbers, superscript numbers

The correct answer is coefficients.

Explanation:

Coefficients are defined as the numbers which are written in front of the atoms or molecules in a chemical reaction. They represent the number of moles of substance in a chemical reaction.

Subscript numbers are defined as the number of atoms of each element present in a compound.

Superscript numbers are defined as the charges of ions reacting in a chemical reaction.

For Example: Dissociation of sodium carbonate into its ions, the equation follows:

The number '2' on the left side written in the subscript of sodium ion represents the number of sodium atoms.

The number '2' on right side written in front of sodium ion represents the number of moles of sodium ions.

The number '(2-)' on right side written in the superscript of carbonate ion represents the charge on carbonate ion.

Hence, the correct answer is coefficients.

b.final

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