PH Sensor Arduino I2C

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,20,4);  // set the LCD address to 0x27 for a 16 chars and 2 line display

int pH = A0;
int buf [10];

float ph (float voltage) {
  return 7 + ((2.5 - voltage) / 0.18) ;
}

void setup () {
  // put your setup code here, to run once:
  pinMode (pH, INPUT) ;

  Serial.begin (115200) ;

  lcd.begin () ;
  lcd.backlight () ;
  lcd. setCursor (0, 0) ;
  lcd. print ("Welcome") ;
  delay (1000) ;
  lcd.clear () ;
}

void loop () {
  // put your main code here, to run repeatedly:
  lcd. setCursor (13,1) ;
  lcd.print ("      ") ;

  lcd. setCursor (13, 2) ;
  lcd.print ("      ") ;

  for (int i=0; i<10;i++)
  {
    buf[i]=analogRead(pH) ;
    delay (10) ;
  }


  float avgValue=0;
  for (int i=0;i<10;i++)
  avgValue+=buf [i];


  float pHVol=(float)avgValue*5.0/1024/10;
  float phValue = -5.70 * pHVol + 21.34;


  lcd. setCursor (0,0) ;
  lcd. print ("pH Formula : ");
  lcd. print (ph (pHVol) , 2) ;
  lcd. setCursor (0,1) ;
  lcd. print ("pH Cal   : ") ;
  lcd. print (phValue) ;

  delay(1000);
}