I tried an experiment at home where I had a $\ce{CO2}$ tank pumping $\ce{CO2}$ into a solution of $\pu{28 g}$ sodium hydroxide in $\pu{200 ml}$ water. The initial $\mathrm{pH}$ was $11.24.$
I expected it to form sodium carbonate and bicarbonate, but instead, the $\mathrm{pH}$ went up to $11.5.$ I should point out that my $\mathrm{pH}$ sensor needed a few minutes of cleaning in distilled water to prevent inaccuracy because the sodium hydroxide particles stuck to it.
Is this supposed to happen, or is my $\mathrm{pH}$ sensor inaccurate? Is there another way to do it? I also found some videos online and in those videos, the $\mathrm{pH}$ went acidic instead of the $\mathrm{pH}$ of sodium carbonate which is between $8$ and $10.$